The study examines how young adult transitions into and out of social roles (i.e., starting or ending a job, a romantic relationship, school) are associated with drinking motives (coping, enhancement, social, and conformity) and alcohol use in a given month. A community sample of young adult drinkers (N = 767; 56.3% female; 59.3% White; Ages 18-23) completed 24 consecutive months of online surveys (N = 15,333 months of data) about the previous month's experiences, social role transitions, and alcohol use. During the 2-year data collection window, participants reported starting/ending a job (10.0%/8.2%), a relationship (2.7%/4.3%), and school (9.2%/17.4%). Between persons, those who more often started jobs were more likely to drink and those who more often ended jobs had higher enhancement motives; those who more often ended relationships were more likely to drink, have a greater number of drinks when drinking, and have higher coping and enhancement motives; and those who more often started relationships had higher conformity motives. Within persons, during months when a relationship ended, participants reported stronger coping motives, and during months when a relationship started, they reported stronger social motives for drinking. During months when a relationship started or ended, participants also reported consuming a greater number of drinks when drinking. There were no differences based on starting or ending school. Young adult social role transitions are associated with concurrent changes in both alcohol use and motives for drinking. Understanding these contextual changes and their concomitant risks is key to providing salient interventions to reduce alcohol-related harm. (PsycINFO Database Record (c) 2018 APA, all rights reserved)