It is well established that young adults are a population at risk for problem gambling and that young adults gamble for various reasons, including positive mood enhancement and negative mood reduction. Although these motives have been identified as important proximal predictors of gambling, the research to date has focused on between-subjects relationships. What is missing is a process-level understanding of the specific within-subjects relations between mood-regulation motives for gambling, mood states, and gambling behaviors. The current study used experience sampling to assess the specific link between gambling motives, mood states, and gambling behavior. Participants were 108 young adults (ages 19-24 years), who completed baseline measures of gambling motives and gambling problems and then reported on their mood states and gambling behavior three times a day for 30 days. Multilevel modeling analyses revealed a significant positive moderating effect for enhancement motives on the relationship between positive mood and amount of time spent gambling and number of drinks consumed while gambling. In addition, problem gambling status was associated with consuming fewer drinks while gambling at higher levels of positive mood, and spending more money than intended at higher levels of negative mood. Unexpectedly, there was only one moderating effect for coping motives on the mood-gambling relationship; low coping motivated gamblers consumed more alcohol while gambling at higher levels of positive mood, whereas high coping motivated gamblers did not change their drinking in response to positive mood. The current findings highlight enhancement motives as risky motives for young adult gambling, particularly in the context of positive mood, and suggest that gambling interventions should include strategies to address positive mood management.