The purpose of this study was to investigate the effects of parent participated aquatic exercise program on parents’ perception of physical activity(PA) participation and the effects on children with developmental disabilities’ PA level, health related physical fitness. 26 couples(child and parent), aged between 9 and 13 years old, participated in the study. Subjects were divided into two groups: parents participated group(n=15), comparison group(n=11). The PA Values and Concerns Survey was used to measure parents’ perceived perception. Qualitative data was collected as well in order to further understand the context of each participant. Actigraph GT3X+ was used to measure PA level. BPFT(Brockport Physical Fitness Test) was used to evaluate the cardiovascular endurance, muscular strength, muscular endurance, and flexibility. Bio-electric impedance analysis was used for body composition. All evaluations were conducted 8 weeks before and after parent participated aquatic exercise program. The data were analyzed by Two-way ANOVA with repeated measure. Significance level was p<.05. As results, Parents’ perceived perception did not show a statistically significant change; however the qualitative data showed changes: parents’ perceptions of children (Discovery of child’s ability, Discovery of the child’s own way of adaptation, and Perception the necessity for child’s PA participation), and parental role of PA participation(Extended parental role, Transition to everyday life). Children?셲 PA level was not increased, and children?셲 health-related fitness was partly improved.