Transgender and non-binary (TNB) individuals are at greater risk of mental health concerns relative to their cisgender peers due to experiences of minority stress. Thus, it is critically important to identify factors that may be protective and buffer the effects of minority stress. This study examined whether romantic relationship involvement and quality buffered effects of TNB minority stress on depressive symptoms and suicidal ideation. A large international sample (n = 1156) of TNB adults (n = 654 partnered; n = 502 single) reported on minority stress experiences, relationship status and quality, and mental health outcomes (i.e., depressive symptoms and suicidal ideation). The effects of victimization and rejection on depressive symptoms and suicidal ideation were attenuated among partnered individuals. However, once relationship quality was considered, the buffering effects of relationship involvement applied only to those in more satisfying relationships; the stress-buffering effects were not observed among those in distressed relationships. Of particular importance, general interpersonal satisfaction did not act as a minority stress buffer, suggesting there may be unique stress-buffering effects of being in a satisfying romantic relationship on depressive symptoms and suicidal ideation. The cross-sectional nature of the current study precludes definitive conclusions regarding causation. These findings suggest that romantic involvement may serve a stress-buffering role for TNB adults, but only when these relationships are satisfying. Our results have important theoretical and clinical implications, and further research is needed to investigate the utility of relationship interventions to buffer the effects of TNB minority stress on depressive symptoms and suicidality. •Being partnered buffers TNB minority stress effects on depression and suicidality.•Buffering effects applied only to satisfying romantic relationships•Buffering effects most evident for interpersonal minority stressors•General interpersonal satisfaction did not buffer minority stress effects.