There is limited research on participation context in studies of physical activity correlates during adolescence. Using an ecological approach, this study explored the association of gender, socioeconomic status (SES), weight status, and physical education enjoyment with participation in organized and unorganized physical activity contexts in a representative sample of Canadian adolescents. Drawing on data from the National Longitudinal Survey of Children and Youth (Cycle 3), we conducted multiple logistic regression analyses to model the associations among the variables of interest. Girls participated less frequently in unorganized physical activities than boys (adjusted odds ratios [AORs] ranging from 0.57 to 0.65, 95% confidence intervals [CIs] range: 0.46-0.72 to 0.52-0.81). Adolescents in the middle and high SES categories participated more in organized physical activity than their peers in the low SES category (AOR = 1.40-1.87, CI = 1.06-1.84 to 1.41-2.47). Obese adolescents were generally less active than their overweight and normal weight counterparts, particularly in unorganized physical activity contexts (AOR = 0.63-0.66, CI = 0.43-0.92 to 0.44-0.99). Physical education enjoyment was consistently correlated with participation in organized and unorganized physical activity when all variables were considered (AOR = 1.58-3.98, CI = 1.22-2.05 to 3.14-5.03). (Contains 3 tables and 1 note.)