Seniors are at particular risk for problem gambling due to lifecycle events such as retirement, loss of a partner, limited income, and normative age-related cognitive decline. In addition to these person-level factors, the environmental context may also influence seniors’ gambling. We analyzed the Ontario Seniors Gambling data (N = 2,103) to explore the effects of person-level, environmental, and person-level by environmental effects of gambling outcomes. Person-level predictors included attitudes towards the benefits and harms of gambling, whether gambling should be legalized, and a set of gambling approach and avoidance motives. Environmental predictors included proximity to the nearest casino, being part of an organized group visiting the casino, and coming alone to the casino. Three outcomes were modeled: frequently gambling at slot and electronic gaming machines (EGMs) which are increasingly favoured by problem gamblers, gambling expenditure, and problem gambling. Older age, male sex, avoidance motives for gambling, and geographic proximity were positively associated with frequent gambling at slot machines and EGMs. Female sex, negative views about the legalization of certain types of gambling, approach and avoidance motives, visiting the casino without an organized group or coming alone, and frequently playing slot machines and EGMs predicted higher gambling expenditure. Problem gambling was more likely in younger unmarried and employed seniors who were born out of Canada. Additionally, problem gambling was also more likely in seniors who considered gambling more beneficial than harmful, endorsed avoidance motives, frequently played slots and EGMs, and had relatively high gambling expenditures. Taken together, these findings clarify linkages between sociodemographic, motivational, attitudinal factors, and environmental factors, on the one hand, and economic and psychosocial gambling outcomes, on the other hand. Finally, the findings converge with extant literature in identifying an association between playing slots and EGMs and problem gambling. These results have implications for policymakers and researchers, and highlight points of intervention to reduce the incidence of problem gambling among seniors in Ontario and beyond.