Compared to heterosexual men, gay and bisexual men (GBM) are at an increased risk of adverse mental and sexual health outcomes. Minority Stress Theory (MST) proposes that GBM experience an increased prevalence of poor mental health outcomes as a result of minority stress. Building upon MST, the Psychological Mediation Framework (PMF) posits that minority stress leads to changes in general cognitive, affective, and social psychological processes, thereby leading to negative mental health outcomes. The present mixed methods study focused on three primary objectives in a sample of 261 GBM: (a) testing the indirect effects of general psychological processes in the relationship between minority stress and poor mental health outcomes; (b) evaluating whether these processes also account for the relationship between minority stress and poor sexual health outcomes; and (c) qualitatively exploring and further clarifying the PMF. Quantitative results provided support for the PMF by demonstrating that experiences of objective stigma were associated with elevations in psychological risk factors, which were in turn associated with adverse mental health outcomes. When each mediator was examined separately, affective processes had a significant effect on mental health outcomes whereas cognitive and social processes were non-significant. For sexual health, the total indirect effect of general psychological mediators in the relationship between stigma and sexual health outcomes was non-significant. However, when mediators were examined separately, cognitive processes did appear to have a significant indirect effect in this relationship, whereas affective and social processes were non-significant. Qualitative results provided partial support for the PMF; many, but not all, of the key components of the model were discussed by participants, and a number of novel themes emerged that expand beyond variables described in the PMF. These findings have important theoretical implications by helping to refine the PMF and future studies of minority stress. Further, by offering a better understanding of the mechanisms linking minority stress and poor health outcomes, this study may help guide future psychological interventions aimed at improving the health of GBM.