Objective To investigate the impact of implementation of the Statewide Medicaid Managed Care (SMMC) program in Florida on access to and quality of primary care for Medicaid enrollees, measured by hospitalizations for ambulatory care sensitive conditions (ACSCs). Data Sources We examine inpatient data obtained from the Agency for Health Care Administration for 285 hospitals in Florida from January 2010 to June 2015. The analysis includes 3,645,515 discharges for Florida residents between the ages 18 and 64 with a primary payer of Medicaid or private insurance. Study Design We use a difference‐in‐differences approach, comparing the change in the incidence of ACSC‐related inpatient visits among Medicaid patients before and after the implementation of SMMC, relative to the change among the privately insured. Principal Findings After implementation of SMMC, Medicaid patients experienced a 0.35 percentage point slower growth in overall ACSC‐related inpatient visits, and a 0.21 percentage point slower growth in chronic ACSC‐related inpatient visits. The effects were significant in counties with above median Medicaid managed care penetration rates. Conclusions Implementing mandatory managed care in Medicaid in Florida leads to slower growth in inpatient visits for conditions that can potentially be prevented with improved access to outpatient care.