Engineer Monkey is a tower in Bloons Tower Defense 5 Deluxe, Bloons Tower Defense Battles Mobile, Bloons Tower Defense 5 Mobile, Bloons Monkey City, and Bloons Tower Defense 6 originally debuting under the name Monkey Engineer. It wields a nail gun that shoots at a quick speed, popping three bloons per shot. With upgrades, the Monkey Engineer can spawn sentries, assisting it with popping power. This is one of the most reliable starting towers in the game and with the help of its sentries, it can solo multiple rounds early on. The Engineer Monkey was added to Bloons Tower Defense 6 on September 17, 2019 as part of the 12.0 update.

An update on Bloons Monkey City on 15th October 2014 added Monkey Engineers and Second City simultaneously. Engineers are unlocked once you reach level 5 on your second city.

Bloons Tower Defense 5Edit

Monkey Engineer

In BTD5, it was first released on BTD5 Deluxe on first release, along with Bloonchipper. It was later added to Bloons Monkey City Flash on September 2014 (?). Later, it was released on all mobile versions of the game. It was never added to BTD5 Flash or Bloons TD Battles Flash.

Path 1Edit

Easy Medium Hard Impoppable

Sentry Gun
Automatically creates sentry guns and deploys them on the ground nearby. Sentries shoot sharp steel pins at the bloons but only last a short time.

$425 $500 $540 $600

Fast Engineering
Engineer increases his build speed, producing sentry guns more often.

$340 $400 $430 $480

Cleansing Foam
Engineer uses a special dispenser to spray down the track with a cleansing foam that removes camo and regen properties. Also pops lead bloons.

$680 $800 $865 $960

Bloon Trap

Creates a powerful bloon trap that destroys all the bloons caught in it. Once full, trap will destroy itself after a short time. If emptied manually, gives you extra cash. Only one trap can be active at a time.

$2975 $3500 $3780 $4200
Total Sell Amount $3844 $4520 $4880 $5424 ($6480 with path 2 upgrades)
Total Cost $4805 $5650 $6100 $6780 ($8100 with path 2 upgrades)

Path 2Edit

Easy Medium Hard Impoppable

9-Inch Nails
Engineer's nailgun upgrades to shoot massive 9-inch nails that can pop 8 bloons at once including frozen bloons (does not affect sentries)

$385 $450 $485 $540

Larger Service Area
Engineer can shoot further and deploy sentries in a larger area.

$555 $650 $700 $780

Adding sprockets to sentries and the nailgun increase their fire rate appreciably.

$470 $550 $595 $660

Activated Ability: Overclock - target tower becomes super powered for 60 seconds.

$11475 $13500 $14580 $16200
Total Sell Amount $10616 $12480 $13476 $14976 ($15840 with path 1 upgrades)
Total Cost $13270 $15600 $16845 $18720 ($19800 with path 1 upgrades)

Tower XPEdit

Level Upgrade at next level Total XP XP to next level
1 Sentry Gun 0 150
2 9-inch Nails 150 400
3 Fast Engineering 550 950
4 Larger Service Area 1,500 1,000
5 Cleansing Foam 2,500 3,200
6 Sprockets 5,700 3,300
7 Bloon Trap 9,000 8,000
8 Overclock 17,000 11,000

Differences Between BTD5 Flash and BTD5 MobileEdit

Technically speaking, Monkey Engineer only appears in Bloons Tower Defense 5 Deluxe, Bloons Monkey City, and all mobile versions of the Bloons TD franchise. However, there are several differences between the Engineer in Flash games (i.e. BTD5 Deluxe and BMC Flash) than in mobile versions of the games.

Buff Bloon Trap no longer loses collection value in later rounds.

Nerf The Monkey Engineer is unlocked at Rank 21 instead of Rank 20.

Nerf Sentry Gun costs more ($450 → $500).

Nerf Faster Engineering costs more ($350 → $400).

Nerf Cleansing Foam costs more ($750 → $800) and no longer has unlimited pierce.

Nerf Bloon Trap costs more ($3000 → $3500) and Monkey Farmers cannot collect full traps.

Nerf If an Overclock is sold, the tower boosted by that Engineer will lose the boost effect while still showing the aura.

Change balloon Pops from the Monkey Engineer's Sentries, Cleansing Foam, and Bloon Traps now count towards the total pop count of the Engineer.

Change balloon Bloon Traps now are emptiable after each round, even when Non-Stop Mode is on. This is not the case in BTDB Mobile, Apopalypse Mode, and Monkey vs Monkey.

Nerf Bloon Traps no longer detect Camo unless the tower is granted Camo detection.

Change balloon Sentries made by an Engineer automatically disappear when the Engineer is sold.

Buff In desktop versions of the games, Bloon Traps only have to be hovered over to be collected, rather than having to manually click on them.

Update History (Bloons TD Battles Mobile)Edit

Engineer is a pretty balanced tower, not too overpowered or underpowered. Sometimes, however, it's given a few buffs to be more suitable for use in Bloons TD Battles Mobile.

Engineer is generally not very popular in normal games (the only semi popular loadouts that use it are Engineer Farm Ninja and Engineer COBRA Apprentice), but it is a quite popular tower in Play With Fire. This is especially the case when utilising the Bloon Trap upgrade for effectively increasing income two-fold (both by bloon income, and from filling up Bloon Traps from sending bloons that will go back to you).


Buff Bloon Traps no longer spawn on unused track in Defend Mode.


Buff Overclock price decreased ($13500 → $11000).


Buff Overclock price decreased ($11000 → $7500).


Nerf Double-speed-tower ability cooldown timer of Overclock now starts upon tower selection, rather than as soon as the screen opens.


Buff Larger Service Area price decreased ($650 → $500).

Buff Cleansing Foam price decreased ($800 → $650).

Change balloon Larger Service Area additional range decreased by 50% (debatable buff/nerf among fans, since Larger Service Area usually does worse for them than it helps to them).


Buff Tower price decreased ($450 → $400).

Buff Larger Service Area price decreased ($500 → $475).

Buff Overclock price decreased ($7500 → $6000).


Nerf Bloon Trap costs more ($3500 --> $3800)


Nerf Bloon Trap now earns only 1.8x more for manual collection. Automatic collection income remains the same.

Bloons Tower Defense 6Edit

Engineer Monkey was first released in Version 12.0, on September 17th 2019. It was teased a few days earlier on Reddit, on September 15th 2019.

Engineer is a Support-class tower.

Path 1Edit

Easy Medium Hard Impoppable Unlock XP

Sentry Gun
Creates temporary sentry guns and deploys them nearby.

$425 $500 $540 $600 160

Faster Engineering
Increased build speed produces sentries more often.

$340 $400 $430 $480 550

Increased sentry gun and Engineer attack speed.

$445 $525 $565 $660 1850

Sentry Expert

Sentries deploy with different damage types based on your need.

$2380 $2800 $3025 $4200 9500

Sentry Paragon

Creates super-powerful but highly unstable sentries.

$27200 $32000 $34560 $38400 30000

Path 2Edit

Easy Medium Hard Impoppable Unlock XP

Larger Service Area
Shoots further and deploys sentries in a much larger area.

$465 $550 $595 $720 170

Nail gun shots do extra damage to MOAB-Class and Fortified Bloons.

$170 $200 $215 $240 500

Cleansing Foam

Sprays foam that removes Regrow and Camo and pops Lead Bloons.

$680 $800 $865 $960 2000

Overclock Ability: Target Monkey becomes super powered for a short time.

$11475 $13500 $14580 $16200 14000


Overclocked Monkeys gain a small but permanent boost each time overclock wears off.

$102000 $120000 $129600 $144000 35000

Path 3Edit

Easy Medium Hard Impoppable Unlock XP

Oversize Nails
Massive nails pop 8 bloons at once, and Frozen Bloons.

$380 $450 $485 $540 150

Pins Bloons in place for a short time when struck.

$185 $220 $235 $240 500

Double Gun

Two guns for twice the fun.

$425 $500 $540 $600 1800

Bloon Trap
Bloon Trap captures Bloons until full. Select to empty full trap for cash.

$2975 $3500 $3780 $4200 11000


Huge Bloon Traps can trap some of the largest Bloons in them...

$51000 $60000 $64800 $72000 40000

Version History (BTD6)Edit

12.0 (compared to BTD5 Mobile)
  • Buff Engineer added to the game.
  • Buff Sentries no longer consume Footprint.
  • Nerf Sentries now have 1 pierce per nail instead of 2.
  • Nerf Bloon Trap now has decreased income gain dependent on round income penalty, similar to BTD5 Deluxe and Monkey City Flash.
  • Change balloon Several changes in path placement of the upgrades. Sprockets is now a Path 1 Tier 3 upgrade, Cleansing Foam is now a Path 2 Tier 3 upgrade, Bloon Trap is now a Path 3 Tier 4 upgrade, and none of these upgrades may be bought on the same tower.
  • Nerf Cleansing Foam now has less pierce (30 —> 10).
  • Nerf Bloon Trap now has a longer placement cooldown whenever trap is destroyed (~1.0s --> ~5.0s) and is limited to 1 per round. The XXXL Trap upgrade can place unlimited Traps still.
  • Change balloon For each round when that trap still stays on the map, Engineer will store another Bloon Trap on itself, and the effect stacks with the number of rounds passing per Engineer. When all Bloon Traps are used during a later round, Engineer won't spawn another until next round
  • Buff Larger Service Area upgrade costs less ($650 --> $550).
  • Buff Sprockets upgrade costs less ($550 --> $525).
  • Nerf Overclock ability now has an initial cooldown of 15 seconds before usage when the upgrade is first purchased.
  • Buff Overclock ability can now target itself.
  • Nerf Overclock ability duration decreases to 45s for towers valued between $15,000-$39,999, and to 30s for towers valued $40,000+.
  • Buff Bloon Trap now traps more RBE (250 --> 500).

Balance ChangesEdit

  • Buff 4xx Sentry Expert Energy Sentry damage increased from 1 to 2
  • Buff 4xx Sentry Expert Bomb Sentry damage increased from 1 to 2
  • Buff 4xx Sentry Expert Bomb Sentry attack rate increased from 1.5s to 1.4s
  • Buff 4xx Sentry Expert Spiked Ball attack rate increased from 1.25s to 1s
  • Buff 5xx Sentry Paragon explosion damage increased from 70 to 85
  • Buff 5xx Sentry Paragon manually sold sentries will now explode with no animation delay
  • Nerf x4x Overclock attack speed buff reduced from +100% to +67% (farms remain 100)
  • Nerf x5x Ultraboost permanent boost reduced to +6.7% for a maximum of +67%
  • Buff 1xx Standard Sentry pierce increased from 1 to 2
  • Buff 4xx Sentry Expert price reduced from $2,800 to $2,500
  • Buff 5xx Paragon Sentry pierce increased from 3 to 5


  • Buff Sentry Expert's Boom Sentry blast radius increased (12 --> 18)
  • Buff Sentry Expert's Boom Sentry attack speed increased (1.4 --> 1.3)
  • Buff 110 Larger Service Area now applies 1/5th the range (+4) to any sentries produced
  • Buff 101 Oversize Nails allows sentries produced by this tower to pop frozen Bloons
  • Buff 101 Oversize Nails now increases sentry pierce by +1
  • Buff 2xx Faster Engineering sentry deployment rate increased further from 7s to 6s
  • Buff 4xx Sentry Expert base range of all sentries increased from 45 to 50
  • Buff 5xx Sentry Paragon explosion radius now scales with sentry radius
  • Buff x4x Engineer Overclock ability active buff state will now be included in save files
  • Change balloon x5x Ultraboost will now apply ‘perma’ stacks upon ability activation rather than expiration

Ninja Kiwi provided a write-up in the 20.0 Patch Notes for the balance changes.

Continuing our efforts to make crosspaths meaningful and fit the style of each path more solidly, a number of crosspath and base level balance shifts were made.

Bug fixes and other changesEdit

  • Change balloon Larger Service Area now increases Sentry deploy range.
  • Nerf Fixed a bug where unupgraded Engineers gained the Deconstruction buff.
  • Nerf Fixed a bug where Bloon Trap granted camo detection and lead poppage to sentries
  • Nerf Engineer Monkey Knowledge prerequisites have been fixed.
  • xx4 Bloon Trap no longer collects for reduced cash when under a Monkey Town
  • Acquisition range is correctly blocked by obstacles on High Finance
  • xx4 Bloon Trap should collect for the correct amounts after resuming save
  • xx4 Bloon Trap will no longer allow bonus traps to be placed when reloading save
  • x4x Overclock can now be targeted by Techbot
  • x5x Ultraboost will no longer trigger while techbotted if no target was previously set
  • 1xx Sentry Gun sentries no longer gain camo detection when a save is loaded
  • 1xx Sentry Gun sentry placement will no longer ignore ‘smart placement’ if the Engineer cannot reach the track
  • 5xx Sentry Paragon should no longer cause a secondary explosion when manually sold
  • xx4 Bloontrap, resolved collection sometimes displaying less cash than it should



  • There is a glitch with the 3-X Monkey Engineer's cleansing foam that if it's engineer is under the range of a X-3 Monkey village the cleansing foam will pop all bloons, not just leads. Same effect with tier 3 specialty building.
  • The Monkey Engineer can build Sentries on the track in BMC Mobile.
  • The Monkey Engineer was added in the Bloons Tower Defense 5 Mobile 1.3 update, along with a new track.
  • In BMC, the 9-inch Nails upgrade costs $700, but in the other games and levels, it costs $450.
  • This tower can be upgraded to use Sentry Turrets (That randomly spawn within his range) and use a Soap Dispenser to spawn foam that removes camo and pops lead. The Sentry Turrets and Dispensers are most likely references to the game Team Fortress 2.
    • The tower itself may also be a reference to the Engineer class in Team Fortress 2, and with the blue colours from the second upgrade on path 1, the Monkey itself resembles a BLU Team Engineer from Team Fortress 2. The red colours from the second upgrade on path 2, the Monkey itself resembles a RED Team Engineer.
    • The icon for a 1/0 Monkey Engineer also seems to be a reference to Team Fortress 2, as its icon is the engineer hollering and striking a sentry violently with a wrench.
    • Probably to avoid either a bad pun or seeming too much like Team Fortress 2, the engineer does not wield a Monkey Wrench, but rather a crescent wrench.
    • The first upgrade in path 2 is a reference to the industrial band, Nine Inch Nails .
    • The super sentries take the reference to the next level. Since they are red and larger, they look much more similar to the red engineer's sentry gun.
    • Another possible reference to the game is its second fourth tier upgrade, although it actually is not an Engineer's ability.
  • A Monkey Engineer with Cleansing Foam doesn't aim with his gun, so the foam can come from behind the monkey.
  • In the mobile games, sentries can appear anywhere, even on the road, water, trees, other sentries, even other towers. In the other games, they only do this when there's no more room for them.
    • They also lose their footprint in BTD6.
  • Monkey Engineer's 1-0 or 2-0 upgrades (sentries) can be considered as a burden to all towers (also includes himself), as it take up spaces so that you have to either sell it or wait until it's gone to place towers on the spot it occupies.
  • They are mentioned in the description of Hotter Cooldowns, even on flash.
  • This tower with the Cleansing Foam upgrade (besides the Monkey Sub's: Bloontonium everlasting ability) is the only tower that makes Regrowth Bloons lose their regen status.
  • A Support Chinook can move Sentries.
  • The tank for the Cleansing Foam is the same as the tank a Glue Gunner has with the Glue Striker upgrade.
  • Spamming 2-3 Engineers or 3-0 while their third tier Specialty Building is activated can beat every single track on Easy, including the Extreme Tracks, if some are influenced by a 2-2 Monkey Village.
  • This is the recommended tower to use in the special mission Full House, as it will deploy sentries when there can be no more towers placed, allowing the player to bypass the maximum amount of towers. This also applies to Random Missions where the Monkey Engineer is available.
  • In Bloons TD 5 Deluxe, a glitch may occur; if an engineer cannot shoot a bloon before the bloon is popped, the engineer may shoot in the direction it is facing without changing direction.
  • Another BTD5 Deluxe glitch involves clicking on a Sentry Gun blanking the artwork. Also, the Go button never shows up and the game cannot continue.
  • The engineer actually has his artwork wrong; when you upgrade the Monkey Engineer to X-2, the icon next to his pop count will appear with the grayish hat for an X-3 Engineer. When you upgrade to X-3, the icon will appear with the red hat for an X-2 Engineer.
  • If the player sells the engineer, his sentries would be gone instantly after selling the engineer (Mobile only).
    • However, any Cleansing Foam from the engineer will remain its full duration.
    • This is not true in Bloons Monkey City Web as both the foam and the sentries will stay its full duration.
  • In earlier versions of the Mobile versions of BTD5 and Bloons Monkey City, a 1-4 Engineer will look like a 0-0 Engineer with the yellow hardhat and no wrench, but a 0-4 and 2-4 Engineer will have the gray hat and the wrench. It has been corrected in Version 1.8.
  • The Engineer and the Spike Factory both use sprockets in their upgrade descriptions.
  • In Bloons Monkey City Mobile, there is a special mission where you must rescue 5 Monkey Engineers by paying $450 each. Engineer cages that have been touched by bloons will make them disappear and not be able to be used in the game. The objective is to rescue at least one Engineer and beat all the rounds in order to unlock it in the player's city.
  • In BMC, when you have Monkey Knowledge of Rank 3 (camo-shooting sentries) they lose their camo detection after upgrading the Engineer to Sprockets.
    • One reason might be that the Sentries are named "SentrySprockets". This could be an indication that they are considered to be a different tower and thus are unaffected by monkey knowledge. This does not happen in BMC mobile.
  • In BMC, the Monkey Engineer pop count only applies to the engineers themselves, however, BMC Mobile's Monkey Engineer pop count applies to every gadget made by the Engineer, that is, the Sentries and Bloon Traps.
  • Sentries inside the range of a Monkey Village will have the effects of it, regardless of whether the Engineer that spawned them is inside the range of the Monkey Village.
  • In Fast-track mode in BTD5 the Engineer will take a long time before building any sentries on the first round which can cause issues if the player primarily uses them.
  • The engineer appears as the icon for Support towers in the Monkey Knowledge screen in BTD6 meaning it was most likely intended to be a launch tower but was not finished in the time frame they wanted to release the game in.
    • The engineer was eventually released in the 12.0 update with a different artwork than the Monkey Knowledge icon.
  • Prior to the teaser, Engineer Monkey information had been leaked online and inside in-game code, including information about the Engineer's upgrades and the associated Monkey Knowledge, respectively.
  • It is possible to beat Impoppable Mode in BTD5 with only Engineers and Super Monkeys.
  • The Sentry Paragon's turrets look like the Upgraded Turrets of the level 4 Engineer's Workshop, only that they are purple instead of red.
  • In BTD6, this is the only tower where all of its tier 2 upgrades cost less than its tier 1 upgrades.

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