Creates temporary sentry guns and deploys them nearby.
~ Official Bloons TD Battles Mobile description.
BTD5 Sentry Gun

Sentry Gun icon as seen in BTD5

Sentry Gun is the first upgrade of path 1 for the Monkey Engineer in Bloons TD 5 Deluxe, Bloons TD 5 Mobile, Bloons Monkey City and Bloons TD Battles Mobile that allows it to create sentry guns within its range. The Sentry Guns shoot nails, and each nail can pop 2 bloons. It is very useful for the early rounds as it acts like several Dart Monkeys all attacking at once. The Monkey Engineer can create up to 3 Sentry Guns with no fire rate upgrades when upgraded to this. However, the Engineer can produce more sentries if it's under the influence of a Jungle Drums Monkey Village, M.I.B. Call to Arms ability, or if the Fast Engineering and/or Sprockets upgrades are bought.




  • Sentry Guns can be sold for $0, and also have a target priority which can be changed. Often Sentry Guns would only be sold to give space for another tower to be placed on.
  • They are effective on daily challenges and special missions where the amount of towers is limited, as they do not affect your total tower count.
  • Sentry Guns are created every 10 seconds and have a lifespan of 25 seconds.
  • The target priority of a sentry will be the same as the target priority of the engineer who spawned it. (tested in BMC and BTD5 Deluxe)
  • When you upgrade the Engineer to Sprockets, any new sentries spawned will have the name "SentrySprockets". These sentries are not affected by Monkey Knowledge. (tested in BMC)
    • In the mobile versions, the sentries are instead internally upgraded 0-3.
  • The Sentries actually might be based off of the Sentry Turret from Valve's Team Fortress 2.
  • The BMC Mobile sentry is missing the "OnlyTargetPlacementLocations": true line of code, causing the sentries to spawn anywhere, including on the track and on water.
  • When a sentry runs out of time, it explodes. The explosion is visually the same as the Splodey Darts one from BTD5.
Community content is available under CC-BY-SA unless otherwise noted.