Background: Many governments worldwide have established guidelines regarding children's physical activity and sedentary behaviors linked to positive health outcomes. While research has established low adherence to these guideline levels, it is unclear whether parents' knowledge, perceptions, and support around these behaviors might be barriers to adherence. Aims: This study examines parents' knowledge and agreement with guideline levels of physical activity, screen time, and sleep time, as well as their support for these behaviors. Methods: Parents of 5-12-year-old children who presented to a regional general practitioner (GP) office in New South Wales (NSW) responded to a survey regarding their child's physical activity, screen, and sleep time, as well as what they believed to be guideline levels, their perceived ideal levels, and the levels of support they provide for each of these behaviors. Results: Parents' perceived ideal levels for their child's physical activity and screen time were more ambitious than government levels and were consistent with sleep time guidelines. There were, however, few associations between parent support levels and children's actual or perceived ideal levels of these behaviors. Discussion: The findings suggest that parents' perceptions of ideal levels of physical activity and sedentary behavior may not hinder adherence to government guidelines. However, inconsistent, or ineffective support strategies can constrain adherence and thus be a viable intervention target.