Co-op Mode

 is a new mode added to Bloons TD 5 in an update that was released on 25th March, 2013. It involves two players cooperating on a randomly chosen game of BTD5 on a randomly chosen map and difficulty, based on the players' choices. Players are limited to placing, controlling, upgrading and selling towers on their half of the map. This can also provide some advantages, such as Dartling Gun control and banana collecting can being separately performed by two players simultaneously.

Money
Players can choose to request cash from their partner, sending them the alert Your partner has requested cash. Their partner can choose to donate cash to their partner whenever they like, up to $500 or their current amount of cash (whichever is less) every time they donate. Donations can be made both ways and are unlimited.

Maps
There is both a new map and an old map for each difficulty:
 * Easy: Z Factor, Alpine Lake
 * Intermediate: Snake River, Haunted Swamp
 * Advanced: The Eye, Cash Money
 * Expert: Castle, Spider Map

Trivia

 * Players who own Premium Upgrades will have them activated, but the other player will not be able to gain access to them.