BACKGROUND Mental health outcomes among HIV-positive gay men are generally poorer than in the broader population. However, not all men in this population experience mental health problems. Although much is known about factors associated with depression and anxiety among HIV-positive gay men, little is known about factors associated with positive mental health. Such knowledge can be useful for optimizing well-being support programs for HIV-positive gay men. METHODS In this study, we examined flourishing, which broadly covers most aspects of positive mental health. A sample of 357 Australian HIV-positive gay men completed a survey on their mental health and well-being, including the Flourishing Scale. Given the lack of previous research, we explored a wide range of psychosocial factors, including demographics, stigma, discrimination, and social support, to identify key factors linked to flourishing. RESULTS The sample showed a similar level of flourishing to those in general population samples. Several independent factors were found to be associated with flourishing outcomes. Those who were most likely to be flourishing tended to have low or no internalized HIV-related stigma, were employed, received higher levels of practical support, had a sense of companionship with others, and felt supported by family. CONCLUSIONS These and other findings presented in this article may be used to help inform strategies for promoting optimal levels of mental health, and its associated general health benefits, among HIV-positive gay men.