To evaluate the relationship between use of primary care-based social needs services and subsequent utilization of ambulatory, emergency, and inpatient services. This retrospective 2012 to 2015 cohort study uses electronic medical record data from an academic pediatric primary care practice that screens universally for social needs and delivers services via in-house social work staff. Logistic regression (N = 7300) examines how patient characteristics relate to practice-based social service use. Negative binomial models with inverse probability of treatment weights (N = 4893) estimate adjusted incidence rate ratios for ambulatory, emergency, and inpatient service use among those who used social services compared to those who did not. Forty-five percent of patients used primary care-based social needs services. This use was significantly greater among those with disabling or complex medical conditions than those without (adjusted odds ratio and 95% confidence interval (CI) of 9.81 [7.39-13.01] and 2.76 [2.44-3.13], respectively); those from low-income versus high-income backgrounds (1.40 [1.21-1.61]); and Blacks and Latinos than Whites (1.33 [1.09-1.62] and 1.29 [1.05-1.59], respectively). Patients who used social services subsequently utilized ambulatory, emergency, and inpatient services at significantly higher rates than those who did not (adjusted incidence rate ratios and 95% CI of 1.54 [1.45-1.63], 1.50 [1.36-1.65], and 3.23 [2.31-4.51], respectively). Primary care-based social needs service use was associated with increased utilization of ambulatory services without reductions in emergency or inpatient admissions. This pattern suggests increased health care needs or access and could have payment model-dependent financial implications for practices.