This study examined interplay between interpersonal trauma (IPT), relationship status, relationship satisfaction (SAT), and partner substance use (PSU), and whether these relationship dimensions moderated associations between IPT and alcohol outcomes. Data came from a longitudinal study of college students (N=9,911; 61%female; 49%White). Precollege IPT increased the likelihood of being in a relationship, while college-onset IPT decreased the likelihood. IPT predicted lower SAT and higher PSU. Individuals with precollege IPT consumed more alcohol than those without IPT, but this was mitigated for those in relationships. Individuals with college-onset IPT consumed more alcohol than those without IPT, and this was more pronounced with higher PSU. Effects changed modestly when controlling for PTSD. Findings suggest timing of IPT impacts its effects on relationship dimensions, and their interactive effects on alcohol. Involvement in relationships, but not relationship satisfaction, buffers against the effects of IPT on alcohol use, while high PSU partner exacerbates it.