Mass participant sport events (MPSEs) have experienced substantial growth both in the amount and types of events offered. The endurance event industry has recently shifted towards non-traditional events, but an exploration of this new type of event is lacking. Accordingly, research is needed to assess the motives of nontraditional MPSE participants. This research was conducted to explore participant motivations to compete in two different MPSEs. Using an online questionnaire, event participants from two different event contexts (i.e., traditional and non-traditional) were examined (N=408). Through a multi-group CFA of the Motivations of Marathoners Scale (MOMS), a revised adaptation of a traditional participant motivation structure was identified. Participant motivations differed across event contexts on several factors, including health orientation, weight concern, personal goal achievement, affiliation, psychological coping, life meaning, and self-esteem. Suggestions for future research and practical implications for marketing and event management are discussed.