A portable shampoo seat adapter for children that is disposed on the seat of a conventional barber or beautician chair with the back thereof adjacent to and below a conventional shampoo wash bowl. A headrest on the back rest of the seat adapter is disposed in front of and above the shampoo wash bowl on which rests the neck of a child. A water run-off guide extends from the neck rest and has a configuration to surround the neck of the child and to provide a path over which water dripping from the child's hair is returned to the shampoo wash bowl.