The purpose of this study was to test (a) whether drinking motives predict event-level drinking on weekend evenings; (b) whether the number of friends present in social situations was associated with drinking on weekend evenings; and (c) whether drinking motives moderate the association between friends present and drinking.We linked individual-level drinking motives (measured at baseline) to event-level data assessed every Thursday, Friday, and Saturday evening over 5 weeks. The number of drinks and male and female friends present in the situation were assessed at 9 p.m., 10 p.m., 11 p.m., midnight, and 1 a.m. In total, 197 young adults (51.3% male) completed 11,516 event-level assessments.Multilevel models by gender revealed that higher enhancement motives predicted a greater number of drinks consumed in a given moment, but only among women. The higher the number of male and female friends present in a situation, the more drinks consumed by both genders. Last, drinking motives moderated the association between the number of friends present and the number of drinks. For women, higher enhancement motives predicted more drinks in situations with more male friends. For men, higher coping motives predicted more drinks in situations with no friends and in situations with more female friends. Lower coping motives predicted more drinks with more male friends. Higher conformity motives predicted fewer drinks with more female friends.Drinking motives appear to moderate event-level factors rather than directly predict drinking on weekend evenings. Depending on the motives for drinking, event-level factors (e.g., friends present in a situation) have a strong effect on an individual's drinking.