PURPOSE: Sickle cell disease (SCD) is associated with high acute healthcare utilization. The purpose of this study was to examine whether Medicaid expansion in California increased Medicaid enrollment, increased hydroxyurea prescriptions filled, and decreased acute healthcare utilization in SCD. METHODS: Individuals with SCD (≤65 years and enrolled in Medicaid for ≥6 total calendar months any year between 2011 and 2016) were identified in a multisource database maintained by the California Sickle Cell Data Collection Program. We describe trends and changes in Medicaid enrollment, hydroxyurea prescriptions filled, and emergency department (ED) visits and hospital admissions before (2011-2013) and after (2014-2016) Medicaid expansion in California. RESULTS: The cohort included 3635 individuals. Enrollment was highest in 2014 and lowest in 2016 with a 2.8% annual decease postexpansion. Although <20% of the cohort had a hydroxyurea prescription filled, the percentage increased by 5.2% annually after 2014. The ED visit rate was highest in 2014 and decreased slightly in 2016, decreasing by 1.1% annually postexpansion. Hospital admission rates were similar during the pre- and postexpansion periods. Young adults and adults had higher ED and hospital admission rates than children and adolescents. CONCLUSIONS: Medicaid expansion does not appear to have improved enrollment or acute healthcare utilization among individuals with SCD in California. Future studies should explore whether individuals with SCD transitioned to other insurance plans or became uninsured postexpansion, the underlying reasons for low hydroxyurea utilization, and the lack of effect on hospital admissions despite a modest effect on ED visits.