Each session of play therapy can be different, but the common aspects are that the therapist holding the session will know how to systematically use play or playful activities to communicate with the child.

Generally, mental health professionals take children into a playroom that has a wide range of carefully selected toys. The toys are chosen because they help children express a variety of feelings and problems. The therapist allows the child to select the toys and the ways that they want to play with them. The therapist pays extremely close attention to the child's actions and feelings, sometimes engages in imaginary play with the child, and sets limits if the child's behavior gets "out of line." In this type of play therapy, called child-centered play therapy, the child's problems or issues usually come out naturally in their play. Thus, part of the therapist's training involves knowing how to interpret the meaning of children's play. This can help the therapist discuss the "root causes" of the problems with the parents and come up with possible strategies that are more likely to work.

Other times in play therapy, the therapist might decide to do a specific type of activity with a child because it will teach the child a skill they need to learn or will help the child understand things better.