Hospital readmission rates are increasingly used as a performance indicator. Whether they are a valid, reliable, and actionable measure for behavioral health is unknown. Using the MarketScan Multistate Medicaid Claims Database, this study examined hospital- and patient-level predictors of behavioral health readmission rates. Among hospitals with at least 25 annual admissions, the median behavioral health readmission rate was 11% (10th percentile, 3%; 90th percentile, 18%). Increased follow-up at community mental health centers was associated with lower probabilities of readmission, although follow-up with other types of providers was not significantly associated with hospital readmissions. Hospital average length of stay was positively associated with lower readmission rates; however, the effect size was small. Patients with a prior inpatient stay, a substance use disorder, psychotic illness, and medical comorbidities were more likely to be readmitted. Additional research is needed to further understand how the provision of inpatient services and post-discharge follow-up influence readmissions.