People who are attracted to individuals of multiple genders (i.e., bi+ people) experience unique minority stressors (i.e., binegative events) that increase their risk for depression and anxiety. Prior research suggests that these associations are mediated by the internalization of negative thoughts, feelings, and stigma about one’s bi+ identity (i.e., internalized binegativity). However, little is known about factors that may protect bi+ individuals against the detrimental effects of binegative events on mental health. This study examined romantic relationship factors as moderators of the association between binegative events and mental health in a sample of cisgender bi+ women using a 28-day diary study and a longitudinal panel design. Cisgender bi+ women in a married or cohabiting romantic relationship (N = 155) completed daily measures of sad and fearful affect, binegative events, event severity, disclosure of events to their partner, and partner’s responsiveness to event disclosures, and completed measures of relationship adjustment, internalized binegativity, and internalizing symptoms (i.e., depressive and anxiety symptoms) at baseline, day 21, and day 28. We used linear mixed models to examine the degree to which disclosure and perceived partner responsiveness buffered the same-day associations between binegative event severity and sad and fearful affect, and used multiple regression and nonparametric bootstrapping to examine the degree to which internalized binegativity at day 21 accounted for the hypothesized interaction between baseline relationship adjustment and binegative events on internalizing symptoms at day 28. Results indicated that participants reported higher sad and fearful affect when they experienced more binegative events throughout the study, and higher than their average sad affect on days that they experienced a binegative event. Among participants who reported any binegative events, reporting higher average event severity was associated with higher average sadness and fear, but within-person associations between event severity and sadness and fear were not significant. Neither disclosure of binegative events to one’s partner nor perceived partner responsiveness to the disclosure were found to moderate any of these associations. Baseline relationship adjustment did not moderate the association between binegative events and internalizing symptoms in the panel study.