Background Expanding access to and utilization of naloxone is a vitally important harm reduction strategy for preventing opioid overdose deaths, particularly in vulnerable populations like Medicaid beneficiaries. The objective of this study was to characterize the landscape of monthly prescription fill limit policies in Medicaid programs and their potential implications for expanding naloxone use for opioid overdose harm reduction. Methods A cross-sectional, multi-modal online and telephonic data collection strategy was used to identify and describe the presence and characteristics of monthly prescription fill limit policies across state Medicaid programs. Contextual characteristics were described regarding each state’s Medicaid enrollment, opioid prescribing rates, and overdose death rates. Data collection and analysis occurred between February and May 2020. Results Medicaid-covered naloxone fills are currently subject to monthly prescription fill limit policies in 10 state Medicaid programs, which cover 20 % of the Medicaid population nationwide. Seven of these programs are located in states ranking in the top 10 highest per-capita opioid prescribing rates in the country. However, 8 of these programs are located in states with opioid overdose death rates below the national average. Conclusions Medicaid beneficiaries at high risk of opioid overdose living in states with monthly prescription fill limits may experience significant barriers to obtaining naloxone. Exempting naloxone from Medicaid prescription limit restrictions may help spur broader adoption of naloxone for opioid overdose mortality prevention, especially in states with high opioid prescribing rates. Achieving unfettered naloxone coverage in Medicaid is critical as opioid overdoses and Medicaid enrollment increase amid the COVID-19 pandemic.