During the first part of the game, you move Zeke around to build a wall around the Zoo. He must jump to avoid any of the wild animals that are loose. Special items will appear on this level when the fuse-like timer at the top of the screen reaches that part. If the timer makes it to the word "End", the current level ends and the game proceeds on to the next. The bonus items that occasionally appear on the screen include mugs of root beer, ice cream sundaes, clover clubs, watermelons, etc.
When the timer reaches a net, one will appear at a certain location on the wall, and if Zeke picks it up, he will be able to capture the animals on the loose and put them back into the Zoo. The net will eventually disappear and the captured animals will try to escape from the Zoo by eating through the wall. Zeke will have to continue building the wall around the Zoo until time is up. At the end of that level, bonus points are awarded for every animal captured. The animals found on this level are snakes, moose, camels, rhinos, elephants, and a lion.
On the second level, Zelda is tied to a palm tree and Zeke must rescue her by jumping upwards from level to level while dodging coconuts thrown by a mischievous little monkey. On each of the ledges there are various foods and drinks that Zeke can collect for extra points. Sometimes, one of the ledges will even have a "Free Game" sign that will grant you a free credit. While Zelda is tied up, she says "Save Me!", and whenever Zeke gets knocked out by one of the deadly coconuts, she says "Oh, No!" If Zeke makes it all the way to the top and rescues her, she says "My Hero!" and a bonus of 5,000 points is awarded.
The third level is the same as the first, but on the fourth level, Zeke must constantly jump over herds of charging animals that come out of the cages at the end of each escalator. Zeke then rides the escalator to get to the next floor. Zeke must get to the second escalator to reach the top floor and rescue Zelda from it. After Zeke has rescued Zelda on the fourth level, the game begins again with an increased difficulty.
Zoo Keeper has examples of:
- Attract Mode: Complete with occasionally letting you play briefly for free to get your attention.
- Cap: The in-game score counter only displays six digits. However, the game will keep track of rollovers and display scores up to 99,999,990 on the high score table.
- Distressed Damsel: Zelda, Zeke's girlfriend. One of the ever-popular "kidnapped by a monkey" variety.
- The '80s: Specifically, 1982.
- Everything Trying to Kill You: Needless to say, there are no friendly animals at this zoo...
- Mischief-Making Monkey: Too small to be classified as a Killer Gorilla, this little simian somehow manages to hold Zeke's girlfriend hostage while menacing the player with a barrage of deadly coconuts.
- One-Hit-Point Wonder: Any physical contact with an animal means doom for Zeke.
- Pinball Scoring: The point values for jumping over animals starts out at 100 points for leaping over only one; jumping over sixteen before landing nets an astounding 30,000,000! Yes, thirty million!
- Player Nudge: Lose your first life without jumping, and the game gives you a free life and suggests you jump to avoid the animals.
- Public Domain Soundtrack: The Sorcerer's Apprentice is heard when the title screen displays.
- Scoring Points: For each animal caged at the end of a round, for jumping over animals that are outside the cage, and for picking up bonus items, to name a few examples.
- Symbol Swearing: Zeke exclaims "#$%&*@!!!!" if he loses a life during the bonus round.