<p>A web-based self-help intervention manual, grounded in psychological flexibility and self-compassion, was developed and examined to address internalized homophobia among sexual minority communities.&#xa0;This two-week randomized controlled trial assessed its efficacy at baseline, mid-program, post-program, and one-month follow-up. Participants were randomly assigned to either an intervention condition (<i>n</i> = 30) or a wait-listed control condition (<i>n</i> = 30). Measures included the Daily Sexual Minority Stressors Scale (DSMS-LWS), Chinese Internalized Homophobia Scale (HIS-C), Multidimensional Psychological Flexibility Inventory (MPFI-24), Self-Compassion Scale–Short Form (SCS-SF), Generalized Anxiety Disorder Scale (GAD-7), and the Patient Health Questionnaire (PHQ-9).&#xa0;Repeated measures analysis of variance indicated significant reductions in minority stress, internalized homophobia, and anxious and depressive symptoms in the intervention group. Significant improvements were observed in psychological flexibility (Cognitive Defusion, Observing the Self, Committed Action) and self-compassion (Mindfulness, Self-kindness, Common Humanity). In the Psychological Inflexibility Model, significant changes were found in Cognitive Fusion, Attachment to the Conceptualized Self, Inaction, and Unclear Values.&#xa0;The intervention effectively reduced internalized homophobia and minority stress, while enhancing psychological flexibility and self-compassion, highlighting the potential of online self-help programs to significantly support the mental health of sexual minority individuals.</p>