The personality trait self-control has been associated with various adaptive outcomes. The objective of this cross-sectional study was to explore whether self-control is associated with self-reported leisure time physical activity (LTPA), Body Mass Index (BMI), muscle-fitness and aerobic fitness among young men. Participants (482 male conscripts; age M = 20) completed a questionnaire and participated in anthropometric measurements in the DefenceNutri Study, and took standard aerobic fitness and muscle fitness tests as part of their military training. Self-control was found to have a positive association with LTPA, aerobic fitness, and muscle fitness, and a negative association with BMI. Self-control predicted aerobic and muscular fitness regardless of BMI, and remained a significant and independent predictor of aerobic fitness (R[superscript 2][subscript adj.] = 0.28, beta = 0.10, p less than 0.05), but not muscle fitness, when LTPA and BMI were controlled for. (Contains 5 tables.)