Bonus levels refer to the fifth level of an Adventure Mode area (x-5). Most of the Adventure Mode variety are sneak peeks of a mini-game or of Puzzle Mode, except for Level 5-5 (level 5-5 was supposed to be a mini-game, except it was canceled). However, when replaying Adventure Mode, the levels are replaced by their mini-game/puzzle counterparts. The level before each of these, the player will receive an item instead of a plant. For example, after level 1-4 the player gets the shovel.
- Level 1-5: Wall-nut Bowling - A slightly easier version of the Mini-game Wall-nut Bowling. The player also meets Crazy Dave on this level, and he teaches him or her how to use the shovel.
- Level 2-5: Whack a Zombie - A slightly easier version of the Mini-game Whack a Zombie. This is the same the second time you play Adventure Mode, instead of being made harder.
- Level 3-5: Big Trouble Little Zombie - The same as the mini-game, but with one fewer wave. The mini-game version has three huge waves, and the bonus level has two.
- Level 4-5: Vasebreaker - The player plays three levels of Vasebreaker, similar to the Vasebreaker in the online version of the game.
- Level 5-5: Bungee Blitz - This is the only Bonus Level that has no mini-game (or Puzzle Mode) counterpart (although it is in the Limbo Page and in the Bonus Games section of Quick Play in versions that have it). In it, hordes of Bungee Zombies drop zombies and steal your plants. The player gets only Chompers, Flower Pots, Pumpkins, and Cherry Bombs.
Items received before the level
- 1-4: Shovel - Allows the player to remove a plant.
- 2-4: Suburban Almanac - Information on plants and zombies.
- 3-4: Crazy Dave's Car Key - Opens Crazy Dave's Twiddydinkies.
- 4-4: Magic Taco - Crazy Dave's Magic Taco. When the player gives it to him, he gives him or her $1,000 and shows him or her new items in his shop.
- 5-4: Watering Can - Unlocks the Zen Garden.
- DSi version: Bacon - Crazy Dave gives $1,000 and shows new items in his shop, as there is no Zen Garden on this version.
- Some players call the Adventure Mode bonus levels "Crazy Dave Levels" because Crazy Dave introduces the gameplay variation for each one.
- While other bonus levels take place in its own area, level 4-5 (Vasebreaker) is the only bonus level that uses another area, which is Night, despite the fact that world 4 is Fog.
- It is also the only Bonus level to be based on a Puzzle Mode.