Negative interactions between romantic partners, such as when one partner criticizes another about their weight, are associated with poor relationship outcomes. The purpose of the study was to examine associations between romantic partner weight criticism, romantic relationship quality, gender, and Latinx young adults’ romantic relationship instability. Participants were recruited from a Qualtrics panel and completed 30-minute surveys online. The sample included 475 Latinx young adults (60% women; M age = 24.80 years, SD = 3.22; 66% Mexican) who reported on their experiences of romantic partner weight criticism, positive romantic relationship quality (e.g., intimacy, affection, nurturance), negative romantic relationship quality (e.g., conflict, antagonism), and relationship instability. Hierarchical regression analyses were conducted to test the study goals. Overall, weight-related criticism was more strongly associated with romantic relationship instability for men than for women. Further, for men, associations between weight criticism and romantic relationship instability were also particularly strong in the context of low levels of negative romantic relationship quality compared to high levels of negative romantic relationship quality.