The purpose of this study was to test a modified conceptual model of the associations between parental supports and physical activity (PA) orientations and the PA behaviors of young children with developmental disabilities (DDs). In total, 135 parents of young children with DDs completed a questionnaire, which consisted of 67 questions. A pathway analysis indicated that tangible and intangible parental supports were significantly associated with PA behaviors in young children with DDs (β = 0.26, p = .01, and β = 0.24, p = .02, respectively). Tangible parental support was positively associated with parents’ PA behaviors and PA enjoyment (β = 0.22, p < .001, and β = 0.13, p = .04, respectively). Intangible parental support was positively associated with parents’ PA behaviors and PA importance (β = 0.19, p = .05, and β = 0.33, p < .001, respectively). In addition, parental PA behaviors and parents’ perceptions of their children’s motor performance were both directly associated with PA behaviors in young children with DDs. These results highlight the importance of parental support and PA orientations in relation to the PA behaviors of young children with DDs.