BACKGROUND: Young adults who drink heavily, including those who simultaneously use cannabis, experience both positive and regretted romantic/sexual experiences. Both gender and past sexual assault severity may also play a role in the valence of romantic/sexual experiences. The current study focuses on day-level correlates of romantic/sexual experiences, assessing whether: (1) number of drinks or simultaneous alcohol and cannabis use (vs. alcohol only) are associated with likelihood of regretted or positive romantic/sexual experiences and (2) past sexual assault severity or gender moderate these associations. METHODS: Two hundred and one young adults (M RESULTS: Consumption of more drinks increased likelihood of both positive and regretted romantic/sexual experiences. Simultaneous alcohol and cannabis use had no effect on positive romantic/sexual experiences. There was a significant interaction between simultaneous use and gender in the prediction of a regretted romantic/sexual experience when controlling for number of drinks. Among women, simultaneous use (vs. alcohol only) significantly decreased likelihood of regretted romantic/sexual experiences. Among men, simultaneous use was unrelated to likelihood of regretted romantic/sexual experiences. Past sexual assault was not a significant moderator of effects of either number of drinks or simultaneous use. CONCLUSIONS: Among heavy-drinking young adults, a greater number of drinks is associated with both more regretted and positive romantic/sexual experiences. Findings highlight a unique protective effect of simultaneous use for women, even when controlling for how much alcohol is being consumed.