This article documents the quality improvement process implemented by HIP Health Plan of New York (HIP) for the behavioral health continuity-of-care measure, Follow-Up After Hospitalization for Mental Illness. This Health Plan Employer Data and Information Set (HEDIS) measure identifies the percentage of members who receive psychiatric follow-up care after their hospital discharge. Studies indicate that post-hospitalization psychiatric follow-up care is an effective method for reducing hospital readmissions. HIP's mental health services department pursued a number of improvement initiatives with this HEDIS measure. The development of a case management unit proved the most effective intervention as compliance rates for post-hospitalization after-care visits improved and hospital readmittance rates declined. These findings provide valuable resource information for behavioral health providers throughout the United States.