Puzzle Mode is a game mode in Plants vs. Zombies that consists of two (three in the iOS and Android versions) separate puzzle types. It is unlocked in Level 4-6 by receiving a present that is dropped by a random zombie in the level. However, the player cannot try out Puzzle Mode until they complete Adventure Mode. In the iOS and Android versions of Plants vs. Zombies, the player must purchase the Vasebreaker, I, Zombie, and Last Stand game packs. Otherwise, they can only play the first level in each section before needing to buy the rest. Both Vasebreaker and I, Zombie cost 150,000 coins, while Last Stand costs 100,000 coins. This mode is replaced by Brain Busters in Plants vs. Zombies 2.
- Main article: Vasebreaker
In this series of puzzles, the player has to use a non-consumable mallet to break open vases pre-placed on the lawn. The vases contain plants, zombies or sun. In order to complete the level, all vases must be broken and all zombies must be defeated. Different Vasebreaker levels have different plants and zombies, but there are some features common to most of them. Most levels feature left-facing Repeaters, and after To the Left, all levels have two green plant-containing vases with a leaf symbol on them. These vases always yield plants. However, most vases are brown with a question mark on it, meaning its content is undisclosed. The sun obtained from the vases can be used to plant Cherry Bomb to help in the game. Additionally, Planterns in Ace of Vase and Vasebreaker Endless show the contents of the vases adjacent to where they are planted. In Ace of Vase and Vasebreaker Endless, there will always be a Gargantuar in one of the vases, and after every streak of ten in Vasebreaker Endless, one more will appear (the maximum amount is nine Gargantuars). An introduction level of Vasebreaker is featured in Adventure Mode also as Level 4-5 and by replayed in game versions with Quick Play. In the iPad version, the player has to purchase this game pack from Crazy Dave.
- Main article: I, Zombie
I, Zombie is a series of puzzles where the player must deploy zombie units to overcome cardboard plants and to get to the end of each row, where there is a brain. It is important to note that cardboard plants are like normal plants in every single way except appearance. The level is won when all the brains have been eaten, or lost when there is not enough sun to place any more zombies on the lawn, all the brains not being eaten, or no zombies being present on the lawn.
In the beginning of the first level, Crazy Dave tells the player that the zombies wanted to practice invading houses, and of course he did not want any plants harmed, so he put cardboard plants on the player's lawn.
- Main article: Last Stand (Puzzle Mode)
In this series of puzzles, which are exclusive to the iOS and Android versions, players are given an initial amount of 3000 (Day and Night levels), 4000 (Pool and Fog levels), or 5000 (Roof and Endless levels) sun. The difference between the mini-game and puzzle Last Stand is that between zombie waves, removing a plant gives a refund of sun equivalent to its cost, although damaged plants are removed without refund (this applies to Pumpkin, Garlic, Wall-nut, Tall-nut and Spikerock) and upgrade plants will only return the cost of the upgrade itself (for example, if the player removes a Gold Magnet, they will only get 50 sun from the Gold Magnet, and not the additional 100 sun from the Magnet-shroom). Also, the player is forced to use a predetermined selection of plants.
- The music playing during I, Zombie and Vasebreaker is "Cerebrawl" (by Laura Shigihara). This is because the player is both fighting for the zombies (plants in I, Zombie) and the plants (Vasebreaker) but must also use strategy to win.
- I, Zombie and Vasebreaker both take place at Night, because there are mushrooms used in both modes.
- I, Zombie is a reference to the book and movie I, Robot.
- The TV series IZombie could possibly have gotten the inspiration for its name from I, Zombie.
- If the player completes a Vasebreaker level that has been already done, the money bag gives two gold coins, but in the I, Zombie levels it brings five gold coins, making I, Zombie a more efficient replay-type way to get gold coins.
- I, Zombie and Vasebreaker appear as separate game modes in the Windows Phone 7 version.
- The cardboard plant sprites in the Nintendo DS version of I, Zombie use the same sprites as the normal plants.
- The cardboard plants on the iPhone version look a little more realistic and lean slightly.
- There are ten achievements about Puzzle Mode. Three are about Vasebreaker (Smashing!, China Shop, and Gotcha!). Three are about I, Zombie (I, Win, Better Off Dead, and Where the Sun Don't Shine). Three are about Last Stand (Still Standing, The Stuff of Legends, and Hammer Time!). The last one is about the whole Puzzle Mode, Think Hard, which is only acquired on the DS version.
- Conveniently, Puzzle Mode cannot be activated until beating Level 4-5 on most versions, after obtaining Crazy Dave's Magic Taco.
- Vasebreaker is the only mode from Puzzle Mode so far to make a return in Plants vs. Zombies 2.
- Most of the levels' names are either puns or references to pop-culture media.