OBJECTIVES: The market for chronic hepatitis C (HCV) treatment has changed rapidly. New treatments offer high cure rates, fewer adverse effects, and shorter treatments-but also increased costs per therapy. The objective of this study was to compare adherence and cost between HCV patients included in an enhanced prior authorization and management program (PAMP) versus no intervention in Medicaid members undergoing treatment. DESIGN: A retrospective study using longitudinal panel data assessed differences in adherence and costs associated with implementation of the PAMP from the payer perspective. The PAMP included case management, patient education, pharmacy counseling, and medication adherence. Multivariable generalized estimating equations were used to assess associations between program and outcomes. SETTING AND PARTICIPANTS: Patients with HCV enrolled in a state Medicaid program receiving or requesting HCV treatment from January 2014 to November 2015. OUTCOME MEASURES: Outcomes included medication adherence, treatment gaps, and pharmacy and total direct costs after controlling for demographic and clinical factors between those in the PAMP and those in the preintervention period. RESULTS: There were 384 Medicaid members included (156 pre-PAMP, 228 post-PAMP). Overall adherence was high regardless of PAMP intervention, although an adjusted 1.086-fold increase in medication possession ratio (MPR) was observed with the program and a 2.732-fold higher odds of adherence above 80% (P < 0.05). Members in the program had 0.358 times lower adjusted odds of a greater than 3-day treatment gap, and pharmacy-related costs were 0.940 times lower (P < 0.05); no difference was observed in total medical costs (P = 0.333). CONCLUSION: This enhanced Medicaid program was associated with increased adherence to HCV therapy, decreased treatment gaps, and decreased pharmacy-related costs compared with the preintervention period. Because challenges exist if patients fail HCV treatment or if viral resistance emerges, ensuring high adherence and persistence remains key. Continued work is needed to develop and assess enhanced management programs for this population.