Purpose Homeless gay and bisexual (G/B) men evidence unmet physical and mental healthcare needs. To gain a greater understanding of predictors of unmet physical and mental healthcare needs, the purpose of this cross-sectional study was to understand correlates of baseline self-reported unmet physical and mental healthcare needs among stimulant-using homeless G/B men (N=422, 18-46 years of age). Methods A structured questionnaire was administered at baseline; data were collected from October 2009 to January 2013. The study was approved by the University of California Human Subjects' Protection committee and the Friends Research Institute Human Research Protection Committee. Results Logistic regression revealed that those who self-reported ever being married, being in fair or poor health and in moderate-to-very severe pain were more likely to experience unmet need for physical healthcare. Those who self-reported ever being married, being in fair or poor health and in moderate-to-very severe pain were more likely to experience unmet need for physical healthcare. In terms of unmet mental health needs, those who self-reported moderate-to-very severe pain and/or those reporting having sex while high were more likely to report unmet need for mental healthcare. In contrast, those reporting receiving social support from others were less likely to have an unmet mental healthcare need. Conclusions Research implications will be discussed as they relate to access to physical and/or mental healthcare needs among this vulnerable population.