Aim: This study examined associations between leisure-time activities and gambling participation respectively problem gambling among adolescents in Sweden. Furthermore, the study examined sex differences and the degree of possibly confounding factors. Methods: The data was obtained from European School Survey Project on Alcohol and Other Drugs, 2019 (n=1,911). Chi2-tests and logistic/multiple logistic regressions were used to analyze the data. Results: Unstructured leisure-time activity was robustly positively associated with gambling participation, structured leisure-time activity was weakly negatively associated with gambling participation among students. Unstructured leisure-time activity was moderately positively associated with problem gambling, structured leisure-time activity was weakly negatively associated with problem gambling among students. Unstructured leisure-time activity was strongly positively associated with gambling participation, structured leisure-time activity was strongly negatively associated with gambling participation for boys. Unstructured leisure-time activity was weakly positively associated with gambling participation for girls. Parental monitoring, school adjustments and externalizing behaviour problems affected the association between unstructured leisure-time activity for students respectively boys. Conclusion: Associations were found of varying extent between leisure-time activities and gambling participation respectively problem gambling. More and stronger associations were found for boys than girls and possibly confounding factors affected the association between unstructured leisure-time activity and problem gambling to some degree.