Depression is frequently comorbid with diabetes; however, less is known about this comorbidity in socially disadvantaged populations. This cross-sectional study examined depressive symptomatology among 424 patients with prediabetes or type 2 diabetes mellitus at a federally qualified health center. Prevalence of clinically significant depressive symptoms was assessed using the World Health Organization Five-Item Well-Being Index. The majority (67.7%) endorsed depressive symptoms, with greater prevalence among middle-aged adults (45–64 years) than younger or older counterparts. More women than men endorsed depressive symptoms. Findings suggest the need for routine depression screening in both prediabetes and type 2 diabetes mellitus, particularly among middle-aged and low-income individuals.