BACKGROUND: Gay, bisexual, and other men (GBM) who have sex with men living with HIV in serodifferent couples (one partner living with HIV, the other HIV-negative) may encounter unique sexual health challenges. This study aimed to explore their definition of sexual health that could improve service provision. METHODS: We interviewed 10 gay-identified men living with HIV from 2017 to 2019 as part of CTNPT013, a study on the sexual health of HIV serodifferent GBM couples conducted at two HIV-specialised clinics in Montreal, Canada. Participants partook in semi-structured interviews on the meaning of sexual health. We performed a content analysis of interview transcripts, coding them according to the 10 dimensions of Robinson's Sexual Health Model. RESULTS: Mean age of interviewees was 35.4years (s.d.,10.2; range, 20-53). Every dimension of Robinson's model was spontaneously evoked, except for body image and spirituality. All men indicated intimacy/relationships (e.g. sexual agreements) and sexual health care/safer sex (e.g. HIV management, risk behaviours) as relevant aspects of sexual health. Other dimensions included: positive sexuality (n =7), such as pleasure and enjoyment during sex; talking about sex (n =5), which mainly concerned HIV disclosure; sexual functioning (n =4); challenges to sexual health (n =3), including substance abuse; and culture/sexual identity (n =3). Two participants (n =2) cited masturbation/fantasy. CONCLUSIONS: This study emphasises the multi-faceted nature of sexual health for gay men with HIV in serodifferent couples and the pivotal roles of relationships, HIV, risk management (e.g. via health care, knowledge), and positive sexual experiences. These dimensions could be considered in sexual health promotion interventions targeting this population.