An estimated one in three gay and bisexual (GB) male couples receive a prostate cancer (PCa) diagnosis over their life course with limited understanding of the impacts on their relationships. Psychological distress related to PCa diagnosis and treatment-related side effects have been shown to disrupt established GB partnership dynamics. Communication barriers often develop within GB relationships affected by PCa, further exacerbating couple tensions, isolating partners, and lowering quality of life for both patients and partners. In order to elaborate on these phenomena following a PCa diagnosis, we conducted focus group discussions with GB men in relationships. Men were recruited nationally through PCa support groups, and after completing consent procedures, they were invited to one of two focus group discussions conducted through video conference. Topics discussed included the diagnosis and medical decision making pertaining to PCa; healthcare provider experiences; the emotional, physical, and sexual impact of PCa diagnosis and treatment; sources of support and appraisal of resources; and partner involvement and communication. There were twelve GB men who participated in focus group discussions that were audio-recorded and transcribed, and analyzed using a thematic approach. GB couple experiences with PCa during and after treatment choice and recovery identified common patient–provider communication barriers. In particular, GB men reported difficulties in disclosing their sexuality and relationship to their providers, limiting conversations about treatment choice and partner engagement in care. Both patients and partners experienced times of being alone after treatment, either by choice or to give space to their partner. However, partners often did not explicitly discuss their preferences for being alone or together, which resulted in partners’ disengagement in their relationship and the prostate cancer healthcare process. This disengagement could blunt the notable PCa survival benefits of partnership for GB men.