Understanding parental physical activity support in parents of children with developmental disabilities across two different countries

•South Korean parents of children with developmental disabilities (DDs) had lower parental support than American parents of children with DDs.•The theory of planned behavior was capable in explaining parental support processes in parents of children with and without DDs.•Attitude towards parental support was the strongest antecedent for intention to support physical activity of children with and without DDs. It remains unclear if there is a difference between parental physical activity (PA) support in parents of children with developmental disabilities (DDs) and parental PA support in parents of children without DDs across countries. The purposes of the current study were to examine parental PA support in parents of children with and without DDs from the United States and South Korea and to examine their parental PA support mechanism based on the theory of planned behavior (TPB). An online survey was used to measure demographic information, parental PA support, and four constructs of TPB in parents with and without DDs in the two countries (n = 277). One-way analysis of variance was used to compare parental PA support and the TPB constructs among the participants. Two separate path analyses were performed to examine associations between the TPB constructs and parental PA support in American parents of children with and without disabilities and South Korean parents of children with and without disabilities. Parental PA support was significantly higher in American parents of children with DDs than in South Korean parents of children with DDs. Intention was significantly associated with parental PA support, and attitude was the strongest predictor for intention in both pathway models. The difference in parental PA support between American parents of children with DDs and South Korean parents of children with DDs may exist. TPB-based intervention may be necessary in order to increase low parental PA support in South Korean parents of children with DDs.