In the game, players attempt to prevent "Bloons" (the in-game name for balloons) from reaching the end of a set course by placing towers or road items along it that can pop the bloons in a variety of ways, typically by using the power of monkeys, magic, or technology.

MOAB-class bloons are in the shape of a blimp and consist of: the MOAB (Massive Ornary Air Blimp), the BFB (Brutal Flying Behemoth), the DDT (Dark Dirigible Titan), the ZOMG(Zoh-my-gods) (Zeppelin Of Mighty Gargantuaness), and the BAD (Big Airship of Doom).

[9] Every tower can be upgraded to increase power and other capabilities by spending the in-game currency, known simply as 'money', which is earned by popping bloons and at the end of each round.

The higher the difficulty the player plays on, the fewer lives they have and the more each tower and upgrade cost.

[8] This version had extra maps styled in snow and beach themes,[20] and included OpenFeint achievements.

[3] Another version of the game, simply titled Bloons TD, was released for DSiWare in 2011, containing 50 rounds to complete.

[24] The gameplay underwent changes including a graphical update, the ability to save the current game, and the introduction of an unlock-based leveling system.

The proprietary version of BTD5 was released on iOS worldwide on November 15, 2012, for iPhones and iPods with improved graphics and additional upgrades, tracks, towers, and bloon types.

[32] Bloons TD 5 Deluxe was released on January 27, 2012, for USD$19.99 during the promotional pre-order period.

[34] As with previous games of the series, the player has to protect the exit(s) against enemy Bloons by using various monkeys and monkey-operated machines placed in strategic locations to fight them off effectively.

[35] Compared to earlier versions of the series, there is a wider variety of different towers and their upgrades.

The iOS, Android, and Steam versions have 15 languages: English, Arabic, Danish, Finnish, French, German, Italian, Japanese, Korean, Norwegian, Portuguese, Russian, Spanish, Swedish, and Turkish.

[40] Unlike all earlier games, Bloons TD 6 does not have a Flash-based counterpart on the Ninja Kiwi website.

Bloons TD Battles was released on December 12, 2012,[55] and later to Android and iOS platforms in-between November 5 and 6, 2013, respectively.

[58] In "Defense" mode, the players play a natural game with the screen split vertically.

Players earn XP for the city by capturing tiles, completing missions or building towers.

They also unlock permanent boosts (Special Items) to attack speed or pierce for specific towers or how long their effect lasts like the Glue Gunner.

In mid-2014, Ninja Kiwi released a new mode known as Contested Territory, a mini-game which offers bonus rewards, and pits players against each other, all of whom compete to survive the most rounds for the longest time on a trickier-than-normal track.

[64] Bloons Adventure Time TD is a crossover game between Ninja Kiwi's Bloons TD series and Cartoon Network's Adventure Time series that was announced via the Cartoon Network International News Site and the Ninja Kiwi blog on March 8 and 9, 2018, respectively.

The game features characters from Cartoon Network's Adventure Time such as Jake the Dog, Finn the Human, and Princess Bubblegum as well as new monkey heroes like Max, Cassie, and C4 Charlie.

[67] It was first leaked in Ninja Kiwi's YouTube video for Bloons TD 6's 24.0 update, on an iPad on the side.

[73] Reaching the maximum arena, Hall of Masters, allows the player to rank up on the game's public leaderboard.

[75] 2010 Wii: 21/100[77] Shortly after the release of Bloons Tower Defense, Lore Sjöberg of Wired described the game as cheerful and addictive, calling it "pop culture at its best".

[18] IGN editor Daemon Hatfield said that he thought Bloons TD 3 succeeded in standing out in the crowded genre by having sufficient core game mechanics and adding an individual twist.

[82] The game's iOS version received mixed reviews with some authors praising the unique towers and good gameplay, though the user interface, controls, and lack of leaderboards were criticized.

"[22] Eurogamer's Kristan Reed gave the PSP version 8/10, describing it as "transfixing", though he said that the music appeared to be designed to "drive you insane".

[19] GameZebo editor Jim Squires gave Bloons TD 4 a 3.5/5 rating, praising it on its well designed maps and towers and for having a large amount of content, but he criticized the game for not "bringing anything new to the genre.

"[24] GamePro editor Ryan Rigney gave Bloons TD 4 a 2/5 rating, stating that it had the same Bloons Tower Defense gameplay as the previous titles, and "the screen eventually gets so hectic that it's no longer fun to play"; an issue which many other reviews also responded negatively to.

[88] Bloons TD 6 received praise for its extended gameplay variety, but has also been criticized for its lack of replayability despite the increased number of unique elements in the game.

[89] The success of the Bloons TD franchise had been given praise by digital investment company Modern Times Group, with special note on Ninja Kiwi's continuous work to "pioneer" the tower defense genre in an economically viable but quality format.