Age play is a type of role-play in which one or more partners acts as though they are a different age than they really are. Props and clothing - such as ruffled dresses, diapers, children's toys and even cribs - may be used during age play, and this fetish can be sexual or non-sexual. If it is sexual, it's not uncommon for incestuous elements to be incorporated into the role-play. Some examples of this include when an "older" age player assumes the role of an older relative, such as a mother, father, aunt, uncle or sibling.

Although a person in an age play scene may act as if they are older than they are, it is more common for someone to act much younger than they really are. For example, it is more common for one partner to act like a baby, child, adolescent, or teenager. Infantilism, incest fetishes, and Daddy's girl fetishes are all common forms of age play.

Age play - particularly age play involving a person assuming the role of a small child - is often widely misunderstood. Contrary to what some may believe, age players are not pedophiles, and they are not interested in sexual relations with children. Individuals that assume the roles of children find comfort in this form of role playing because they get to express their childish feelings and relinquish their responsibility to another person. The age players who assume the role of the older partner get the satisfaction of teaching, caring for and comforting their "younger" partner. Overall, age play relationships are very warm, comfortable and fulfilling for all parties involved.