To resolve the mixed findings on the link between social anxiety (SA) and alcohol use, studies have examined the role of post-event processing (PEP), i.e., negative thinking about past social events. In a sample of 18–30 year olds (82% female) high (n = 40) and low (n = 49) in SA, the current 21-day study assessed the effect of PEP after social drinking events on subjective intoxication at the next social event. The moderating role of SA severity was tested. Compared to the low SA group, the high SA group reported overall more PEP but similar intoxication levels. Multilevel models supported a SA by PEP interactive effect on next-event intoxication, but for the high SA group only. Conditioned slopes revealed that within the high SA group, at − 1 SD elevated PEP predicted increased next-event intoxication. Thus, for those ‘moderate/high’ in SA, PEP after social drinking may increase risk for alcohol misuse.