This study examines the role of self-regulated learning (SRL) skills in physical activity (PA) among Hong Kong Chinese (HK) and Scottish adolescents. Methods Using a cross-sectional design, 480 HK (aged 11-19; mean age = 14.93 years, SD = 1.77, male = 61.3%) and 411 Scottish, aged 12-16 years (mean = 13.84; male = 47.9%) healthy adolescents participated in this study. PA was measured with the Godin Leisure-Time Questionnaire (Godin & Shephard, 1985). SRL was measured for Chinese (SRL-SRS-C; Pitkethly & Lau, 2015) and British adolescents (SLR-SRS; Toering et al., 2012). Results Moderate-to-vigorous intensity PA was significantly higher among Scottish (M = 48.58; SD = 26.01 p= .0005) compared to HK adolescents (M = 31.14; SD = 22.26). All SRL variables significantly explained a small amount of variance in moderate to vigorous intensity PA, in HK (∆R 2 = .021, F(2,461) = 6.320, p = .005) and Scottish (∆R 2 = .020, F(2,376) = 8.427, p = .013) adolescents, reflection was a significant predictor (HK p = .027; SC p = .003). Conclusions In both cultures, higher self-regulating adolescents, may be more likely to engage in higher levels of PA. SRL has a significant impact on PA; and of all the SRL variables, reflection plays a key role in students engagement in PA. Background Globally, four out of five adolescents do not achieve recommended levels of physical activity (PA) (Hallal et al., 2012). Regular participation in PA is associated with a decreased risk of cardiovascular disease (Warburton et al. 2006), obesity and improvements in psychological functioning in adolescents (Biddle & Asare, 2011). As activity levels track from adolescence to adulthood (Malina, 2001; Telama et al., 2005) young people are at risk