Context: Multimorbidity (≥2 chronic diseases), is a major public health problem that is associated with lower health-related quality of life and increased costs for patients, their caregivers, and public programs. Despite rapid advancements in multimorbidity research, there is comparatively little work done to understand multimorbidity among safety-net populations in the United States, many of whom receive care in community health centers (CHCs). Little is known about the prevalence and patterns of multimorbidity in this population, especially in the presence of mental health disorders. Objective: To evaluate the prevalence of multimorbidity combinations and socioeconomic correlates in a nationally representative sample of CHCs. Study Design: Retrospective cohort study. Setting: We used electronic health record (EHR) data from 820 CHCs in 16 states from the OCHIN practice-based research network. Encounter data were queried for patients ≥45 years of age who had at least one ambulatory care visit between March 1, 2015 and September 30, 2018 (n = 85,735). Outcome: Chronic disease indicators for each of the 20 chronic diseases in the Health and Human Services Multiple Chronic Conditions (HHS MCC-20) framework for operationalizing multimorbidity are used to construct two binary multimorbidity combination indicators for: (1) patients with physical-only multimorbidity (≥2 physical conditions), and (2) patients with mental/mental-physical multimorbidity (≥2 mental or ≥2 mental and physical conditions). Results: 70,672 patients seen during the study period have at least one of the HHS MCC-20 conditions of interest and among these patients, 79% have multimorbidity (n=55,686). Of patients with multimorbidity, 54% have mental/mental-physical multimorbidity and 44% have physical-only multimorbidity. Hispanic patients (physical-only= 25%, mental/mental-physical=14%) were more likely to have physical-only conditions than Non-Hispanic white patients, who had relatively higher prevalence of mental/mental-physical conditions (physical-only= 58%, mental/mental-physical=71%). Conclusion: The burden of multimorbidity among a population of adults seeking care in the safety-net is high, particularly with regard to the younger age distribution of the population examined. More than half of our study sample have mental/mental-physical multimorbidity, with vast implications on the kinds of services and coordination of services needed to address chronic care needs in the safety-net.