Objectives. To examine whether referral for social determinants of health (SDH) needs decreases psychological distress and posttraumatic stress disorder (PTSD) symptoms and improves level of functioning and quality of care among diverse adults. Methods. Data are from control participants (n = 503 adults) in a randomized controlled trial testing a mental health intervention in North Carolina and Massachusetts. We fitted multilevel mixed-effects models to repeated assessments (baseline, 3, 6, and 12 months) collected between September 2019 and January 2023. Results. After referral to services for trouble paying utility bills, participants reported lower PTSD symptoms. Participants reported better quality of care when receiving referrals to mental health care. After adjusting for income and employment status, we found that participants who were referred more often also had lower PTSD symptoms and better levels of functioning. Conclusions. Referrals for certain SDH needs might decrease PTSD symptoms and improve self-reported quality of care and functioning. However, referrals alone, without ensuring receipt of services, might be insufficient to affect other mental health outcomes. Research is needed on training and providing care managers time for offering interpersonal support, securing services, and understanding agencies' contexts for addressing high SDH needs. (Am J Public Health. 2024;114(S3):S278-S288. https://doi.org/10.2105/AJPH.2023.307442).