All children and youth require ample physical activity (PA), low levels of sedentary behaviour (SB), and adequate sleep to stay healthy. Children and youth living with disabilities (CYWD) tend to have fewer opportunities for participation in PA and outdoor play compared with their typically developing peers. In turn, CYWD are typically less active and more sedentary, on average, compared with their peers. The COVID-19 pandemic reduced opportunities for many children and youth to participate in PA and outdoor play. The purpose of this study was to assess parent-perceived changes in PA (including outdoor play), SB (including screen time), and sleep quality and quantity, due to COVID-19 and related restrictions, in a national cohort of Canadian CYWD. We recruited parents of school-aged CYWD (N = 151) in May 2020. In an online survey, parents reported their child’s previous 7-day PA, SB, and sleep, as well as perceived changes in their child’s movement and play behaviours due to COVID-19 and related restrictions. Parent-perceived parental support for their child’s movement and play behaviours during the pandemic was also assessed. We used descriptive statistics to describe the child’s movement behaviours and assessed the association between movement behaviours and parental factors using Pearson and point-biserial correlations. Few (5.3%) CYWD met PA recommendations and 13.2% met screen time recommendations during the acute period of the COVID-19 pandemic. More CYWD (66.2%) were meeting sleep recommendations. Overall, only 1.3% of CYWD were meeting the combined movement guidelines. Parent encouragement was positively associated with the child’s outdoor PA (0.23), wheeling, walking, and biking (0.19), indoor PA (0.16), and family-based PA (0.26). Parental co-play was similarly positively associated with the child’s outdoor PA (0.26), wheeling, walking, and biking (0.39), indoor PA (0.16), and family-based PA (0.26). Parents perceived their CYWD to be less active and more sedentary as a result of COVID-19 and the related restrictions. Parents of CYWD have an important role in encouraging healthy movement behaviours. Return to movement and play post-COVID guidelines should include tailored strategies for CYWD and their families to mitigate the negative impacts of the pandemic.