Limited research has examined the mental health of individuals experiencing homelessness in Hawai'i, which bears the nation's second highest homelessness rate. Mental health, substance use, treatment need, and health data were collected from 162 unhoused individuals in Hawai'i County by visiting community locations where they congregate (e.g., beaches, vacant buildings). 77% of participants were Native Hawaiian/Pacific Islander (NH/PI) with participants demonstrating severe rates of mental and substance use disorders including 57% experiencing major depressive disorder (MDD), 56% experiencing generalized anxiety disorder (GAD), and 64%, 74%, and 12% experiencing alcohol, methamphetamine, and opioid use disorders, respectively-heightening overdose risk. Treatment need was high (62%) but health was poor (85% reporting fair/poor health), with MDD and GAD predicting reduced general health (p < 0.05). Study findings indicate Hawai'i unhoused individuals are disproportionately Indigenous NH/PI, enduring striking mental and physical health disparities that may be reduced by increasing access/utilization of community mental health programs/services.