Background: Sexually and gender diverse people affected by cancer (SGDc) experience significant disparities and minority stress across the cancer continuum, alongside high levels of unmet psychosocial needs and limited access to affirming support groups. Existing reviews and equity‑focused frameworks have called for SGDc interventions that centre queer and trans experiences, yet few evaluated models exist in psychosocial oncology. Methods: We conducted a pragmatic quality improvement project within the SGDc Program at Princess Margaret Cancer Centre to develop, implement, and evaluate QUEERMUNITY, a queer‑affirming psychotherapy support group for SGDc patients informed by a gender, sex, and relationship diversity (GSRD) framework. A pre‑implementation needs assessment survey of SGDc patients (n = 19) assessed supportive care priorities, including interest in queer‑specific groups. In response, we launched QUEERMUNITY and invited group participants (n = 31) to complete a one‑time cross‑sectional post‑implementation survey assessing perceived impact on safety, relevance, coping, community, and overall satisfaction, supplemented by qualitative feedback and facilitator observations. Results: In the needs assessment, 15 of 19 respondents (52.6-78.9%) rated "patient support groups specifically for 2SLGBTQIA+ patients and caregivers" as important or very important; adolescent/young adult and older‑adult 2SLGBTQIA+ groups were similarly prioritized. Dedicated SGDc‑specific professional supports (psychiatry, psychology, social work, and other healthcare providers) were endorsed as important or very important by 73.7-89.5% of respondents. One year post‑implementation, 25 of 31 QUEERMUNITY participants completed the survey (80.6% response rate). 91.3% reported feeling safe, comfortable, and inclined to continue engagement, with 95.7% recommending the group to others and rating strong satisfaction regarding community, support, queer joy, and pride.. Qualitative feedback highlighted the value of an explicitly queer‑centred space for discussing cancer, identity, and chosen family; relief at not navigating cis‑heteronormative assumptions; and perceived gains in coping, validation, and sense of community. Conclusions: Pre‑implementation data demonstrated strong demand for queer‑specific support groups and SGDc‑tailored professional supports, and post‑implementation findings suggest that QUEERMUNITY is a feasible, acceptable, and highly valued GSRD‑informed queer‑affirming group intervention in psychosocial oncology. This model offers a practical approach to operationalizing minority stress‑informed, intersectional, and GSRD‑theoretical frameworks in cancer care and may contribute to more equitable, affirming services for SGDc populations.