Objective: This study examined the association between adherence to antipsychotic and cardiometabolic medication and annual use of health care services and expenditures. Methods: MarketScan Medicaid files from 2004 to 2008 were used to evaluate annual cross-sections of patients with schizophrenia and diabetes, hypertension, or hyperlipidemia. Annual adherence to antipsychotic and cardiometabolic medication was defined as a score of at least 80% on proportion of days covered. Logistic regression was used to examine the association between antipsychotic adherence and adherence to cardiometabolic medications. Count data models and generalized linear models estimated health care utilization and health care expenditures, respectively, for outpatient, emergency, inpatient, and overall health services. Results: A total of 87,015 unique patients with schizophrenia received at least one antipsychotic medication. The overall prevalence of any comorbid cardiometabolic condition was 42.9% in 2004 and increased to 52.5% in 2008. Adherence to cardiometabolic medications was significantly greater among patients who were adherent to antipsychotic medications (adjusted odds ratio=6.9). Adjusted annual expenditures for emergency and inpatient care were higher for patients who were nonadherent to either antipsychotics or cardiometabolic medications than for patients who were adherent to antipsychotic and cardiometabolic medications. They were highest for patients who were nonadherent to both groups of medications. Outpatient, medication, and overall expenditures were lower for patients who were nonadherent to antipsychotic medications, regardless of cardiometabolic medication adherence. Conclusions: Among Medicaid patients with schizophrenia, cardiometabolic conditions are common, and adherence to antipsychotics and adherence to cardiometabolic medications are strongly related. Interventions that can improve medication adherence to treatment of both schizophrenia and comorbid cardiometabolic conditions may reduce emergency visits and hospitalizations.