Baby is one of the two roles players can pick when joining Adopt Me!, the other one being Parent. Players can change to the Baby role by either entering the Age-O-Matic in the Nursery, buying and using one in their home, or by clicking the "Switch to a Baby" button located in the bottom right of the dress up menu.
As Babies, players have several needs that periodically appear, similar to Pets. However, babies are more limited in completing certain tasks such as eating or drinking; they have to manually eat or drink numerous times to satisfy their needs, and can't eat off of pet bowls. Babies can also fulfill their food and drink tasks when a nearby family member uses a baby formula, which cures the needs of all pets or babies nearby. While playing as a Baby, players cannot pick up their pets or their family members' pets or babies, even when a stroller is equipped.
Parents can pick babies up or use a stroller to pick them up. Unlike pets, any non-Baby player without a family can pick up a Baby if the Baby isn't in a family. If the Baby is in a family, only Parent family members can pick them up. As a Baby, players can ride players that have the Parent role and are either in the same family as the Baby, or if both the Parent and Baby aren't in a family.
- When a Baby rides a vehicle, the vehicle shrinks to Baby's size, with the exceptions of the Traveling House, the Ice Cream Truck, and the Choo Choo Train. Parents and pets can still ride Baby's vehicle, even if the parent can't fit inside the vehicle.
- A Baby is slightly less than half the height of a Parent.
- A Baby can have all the tasks a pet can, and vice-versa.
- Babies used to spawn in the Nursery, as they do in Legacy Adopt Me.
- When a baby drinks a Grow Potion, they are enlarged to the same size as a Parent.