Recent studies have found that Internalized Heterosexism (IH) is a strong predictor of the psychological well-being of lesbian, gay, bisexual, questioning and same-sex attracted (LGBQ) individuals. To respond to the call for more effective interventions to address IH and its impact on LGBQ individuals, the current study developed and tested an online intervention to reduce IH among gay, bisexual, questioning and same-sex attracted (GBQ) men. A total of 367 adult GBQ males were recruited from nation-wide LGBQ-related sources and were randomly assigned to either the experimental condition (focusing on IH reduction) or the control condition (in which a similarly structured invention focusing on stress management was administered). The differences between the two conditions were compared on variables of IH and affect after the intervention. The findings give preliminary evidence that a brief Web-based intervention can effectively reduce IH among GBQ men. The results also showed that participants as a whole in the experimental condition reported higher levels of positive affect than their counterparts, as a group, in the control condition. In addition, the measured level of involvement in the intervention associated significantly with the effect of the intervention, suggesting that involvement plays a facilitating role. Implications for research and practice are discussed.