Minority stress is the leading explanation for sexual minority women's (SMW) higher rates of, and heavier, alcohol use compared to heterosexual women. Little is known about how both partners' sexual minority stressors impact alcohol consumption in a dyadic context, and even less research has considered these effects at the day-level. This study utilizes dyadic daily diary data to test associations of each partner's sexual minority stress events with drinking outcomes (day-level alcohol use, heavy episodic drinking [HED], and estimated blood alcohol content [eBAC]) among women in same-gender relationships (N = 159 couples). Because high-quality relationships may buffer adverse effects of minority stress on alcohol use outcomes, effect modification was also considered. Results differed across alcohol use outcomes. One's own experience of sexual minority stress was associated with one's own greater odds of drinking that day, OR = 1.33, 95% CI 1.10, 1.61, p = .003, whereas one's partner's experience of sexual minority stress was associated with greater odds of same-day HED, OR = 1.60, 95% CI 1.24, 2.01, p < .001 (no significant effects emerged for eBAC). Relationship functioning was associated with lower eBAC only, B = -0.01, 95% CI -0.01, -0.00, p = .031. No significant effect modification emerged. This initial exploration of how both partners' exposure to sexual minority stressors impact SMW's alcohol use demonstrates nuanced effects across different alcohol outcomes, and is among the first to demonstrate some degree of sexual minority stress contagion on HED.