Purpose: Leisure-time physical activity (LTPA) is known to be associated with positive health benefits, but the role of occupational physical demands remains inconsistent. The purpose of the current study was to assess the relationship between LTPA and work ability in different occupational physical activity (OPA) levels between young adult men. - Methods: We performed physical activity measurements in work and leisure time with the long version of International Physical Activity Questionnaire (IPAQ) and work ability with the Work Ability Index (WAI) in 921 Finnish employed male volunteer participants. The participants were divided into LTPA tertiles I (< 8 MET-h/week), II (8–28 MET-h/week), and III (> 28 MET-h/week) and OPA tertiles I (0 MET-h/week), II (< 64 MET-h/week), and III (≥ 64 MET-h/week). - Results: There was a significant relationship between LTPA and WAI in OPA tertiles (adjusted for age, alcohol consumption, working class status, BMI, and employment years). Moreover, each LTPA tertile showed significant linear associations with WAI (P < 0.001). - Conclusion: LTPA is positively associated with work ability among young adult men. More specifically, the relationships between LTPA and WAI were significantly greater in physically demanding jobs than in more passive jobs. Our results indicate the importance of LTPA, particularly with individuals under higher work-related physical strain.