Men are less likely than women to test for HIV and engage in HIV care and treatment. We conducted in-depth interviews with men participating in One Man Can (OMC) - a rights-based gender equality and health programme intervention conducted in rural Limpopo and Eastern Cape, South Africa - to explore masculinity-related barriers to HIV testing/care/treatment and how participation in OMC impacted on these. Men who participated in OMC reported an increased capability to overcome masculinity-related barriers to testing/care/treatment. They also reported increased ability to express vulnerability and discuss HIV openly with others, which led to greater willingness to be tested for HIV and receive HIV care and treatment for those who were living with HIV. Interventions that challenge masculine norms and promote gender equality (i.e. gender-transformative interventions) represent a promising new approach to address men's barriers to testing, care and treatment.