Several theories posit problematic alcohol use develops through mechanisms of positive and negative reinforcement. However, the literature on these mechanisms remains inconsistent. This may be due to a number of issues including a failure to disaggregate negative mood or a failure to account for mood functioning (i.e., stability in mood). Alternatively, there may be differences in typical postdrinking/evening mood on drinking and nondrinking days, however, this has yet to be fully explored. We examined multiple indices of distinct mood states prior to and after typical drinking onset times on drinking and nondrinking days using ecological momentary assessment. College student drinkers (n = 102) carried personal data devices for 15 days. They reported on mood and alcohol use several times per day. Tonic positive mood was higher on drinking days than nondrinking days prior to typical drinking initiation. After typical drinking times, positive mood was higher on drinking days than nondrinking days. Similarly, negative moods (anxiety, stress, anger, and stress instability) indicated a pattern of lower levels relative to both predrinking mood on drinking days, and matched mood time-points on nondrinking days; though, not all of these differences were statistically different. Results suggest positive and negative reinforcing mechanisms may be at play—though the negative reinforcement effects may manifest through subjectively “better” mood on drinking versus nondrinking days.