Since multiple factors may impact adult levels and patterns of sport participation, this study utilized stages from Green's (2005) sport development theoretical model to examine the structural and individual factors that impact the sport experiences, patterns, and motives of both female and male adults in three different countries: the Netherlands (n=48), the United States of America (n=44), and the Republic of Korea (n=30). Asynchronous online focus groups using semi-structured questions assessed past and current sport participation, barriers and benefits to sport participation, and perceptions of sport delivery systems. The main themes that emerged related to adult sport participation were life-course and transitional dynamics, motivational differences, and sport delivery system impacts. While previous research has typically implicated individual-level factors for differences in sport participation the current study indicates that delivery system level factors are also critical. Systems that are more readily accessible or predictable and those that create social opportunities may be keys to increasing adult sport participation.