OBJECTIVES: Measure the impact of reduced copay intervention on medication usage, healthcare utilization and costs, and health status.   METHODS: A self-insured global healthcare company followed 529 insured members with anxiety and/or depression to determine the impact of waived pharmacy copays for anxiety and depression medications. Primary outcome was pre-post change in medication possession ratio (MPR). Secondary outcomes included initiation of medication, healthcare utilization, medical/pharmacy costs, and percentage of generic medication.  A repeated-measures multivariable model was utilized to measure intervention impact, adjusting for age, gender, number of prescriptions, and comorbidity index.   RESULTS: Unadjusted analysis showed the copay intervention group was significantly more likely to start a new medication (31.4% vs. 29.5%, p = 0.033) and more likely to fill a generic medication (85.1% vs. 80.5%, p < 0.0001), and had higher average MPR (65.4% vs. 60.7%, p = 0.004) than the control group. Healthcare utilization was similar pre-post intervention.  Multivariable adjusted analysis revealed a 4.5% increase in MPR after the intervention (95% CI 2.2% - 6.8%, p = 0.0002).  CONCLUSIONS: Eliminating pharmacy copay for depression and/or anxiety medications was associated with increased medication initiation and adherence. This value-based benefit design could be expanded with additional follow-up to measure longer-term trends and with other medication classes to assess similar impact.