Pet Simulator X is the latest in a series of Roblox role-playing games where you look after and hatch fantasy pets. You work to collect coins with your pets, fuse your pets to upgrade them and unlock new zones to visit. This, in turn, grants access to new pets which in turn opens new areas. It's become popular because of this gameplay loop and the simple polished design. It's one of the most popular Roblox games getting over 1 billion visits a year (in 2022).

Play involves collecting pets by hatching and fusing. To get a pet you need to buy an egg and then hatch it. Pets can then collect gold coins in the game when you click or tap on them. This then allows you to go to new island locations where you can buy different eggs for different pets.

Once you have a collection of pets you can choose to fuse them into new types, using a fusing machine like that found in the beach fantasy area. This results in pets that are rare and have higher stats. In this way you work through the different stages of each type of pet: normal, golden, rainbow, legendary, and mythical. You can obtain rare eggs from specific portals which you unlock with the coins you have obtains in the game.

As with other pet care games in Roblox like Adopt Me, you can also trade pets with other players online. Once both players agree mutually to a trade offer, they can make the swap.