Objective—To explore the relationship between social influences, self-efficacy, enjoyment, and barriers and physical activity. Methods—Structural equation modeling examined relationships between parent and peer support, parent physical activity, individual perceptions, and objectively measured physical activity using accelerometers among a sample of youth aged 10–17 years (N=720). Results—Peer support, parent physical activity, and perceived barriers were directly related to youth activity. The proposed model accounted for 14.7% of the variance in physical activity. Conclusions—The results demonstrate a need to further explore additional individual, social, and environmental factors that may influence youth’s regular participation in physical activity.