Responding to the dramatic growth in Assisted Living Facilities (ALFs), the present study focused on mental health among older residents in ALFs. We assessed the effects of physical health constraints (chronic conditions, functional disability, and self-rated health) and psychosocial resources (social network, sense of mastery, religiosity, and attitude toward aging) on depressive symptoms. A sample of 150 residents (Mage = 82.8, SD = 9.41) from 17 facilities in Florida was used for analyses. Higher levels of depressive symptoms were observed among older residents with a greater level of functional disability, poorer self-rated health, lower sense of mastery, less religiosity, and less positive attitude towards aging. In addition, the linkages between physical and mental health were modified by psychosocial resources. For older residents with more positive beliefs and attitudes (a higher sense of mastery, greater religiosity, and more positive attitudes toward aging), the adverse effects of functional disability or poorer self-rated health on depressive symptoms were attenuated. The protective roles of psychosocial resources against physical health constraints yield important implications for designing prevention and intervention strategies for the mental health of older populations in ALF settings.