Individuals differ in the degree to which they tend to habitually accept their emotions and thoughts without judging them—a process here referred to as habitual acceptance. Acceptance has been linked with greater psychological health, which we propose may be due to the role acceptance plays in negative emotional responses to stressors: acceptance helps keep individuals from reacting to—and thus exacerbating—their negative mental experiences. Over time, experiencing lower negative emotion should promote psychological health. To test these hypotheses, Study 1 (N = 1,003) verified that habitually accepting mental experiences broadly predicted psychological health (psychological well-being, life satisfaction, and depressive and anxiety symptoms), even when controlling for potentially related constructs (reappraisal, rumination, and other mindfulness facets including observing, describing, acting with awareness, and nonreactivity). Next, in a laboratory study (Study 2, N = 156), habitual acceptance predicted lower negative (but not positive) emotional responses to a standardized stressor. Finally, in a longitudinal design (Study 3, N = 222), acceptance predicted lower negative (but not positive) emotion experienced during daily stressors that, in turn, accounted for the link between acceptance and psychological health 6 months later. This link between acceptance and psychological health was unique to accepting mental experiences and was not observed for accepting situations. Additionally, we ruled out potential confounding effects of gender, ethnicity, socioeconomic status, and life stress severity. Overall, these results suggest that individuals who accept rather than judge their mental experiences may attain better psychological health, in part because acceptance helps them experience less negative emotion in response to stressors.