The nature of play and an overview of the stages of play in the first 5 years of childhood are discussed. The core features of sensorimotor, functional, and symbolic play are identified. Vignettes describing how play serves a regulatory function punctuate each section. A conceptual framework for the construct of regulation is presented and counterpointed against the primary sources of dysregulation in young children, including excessive psychosensory stimulation, states of intense emotional arousal, anxiety, and conditions of toxic stress. Factors are reviewed that contribute to the development of self-regulatory capacity, including temperament and constitutional factors, cognitive control in the form of executive function; positive parenting, attachment, and internal representation; and the capacity for symbolization, along with the expected progression of the acquisition of self-regulatory capacity. Specific regulatory functions of play are identified and explicated including play as regulatory practice, novelty and investigation, and roles and rules. The article concludes by summarizing the state of current empirical evidence with regard to play and self-regulation.