Background: In 2018, the Department of Veterans Affairs (VA) issued Notice 2018-08 requiring facilities to complete "case reviews"for Veterans identified in the Stratification Tool for Opioid Risk Mitigation (STORM) dashboard as high risk for adverse outcomes among patients prescribed opioids. Half of the facilities were randomly assigned to a Notice version including additional oversight. We evaluated implementation strategies used, whether strategies differed by randomization arm, and which strategies were associated with case review completion rates. Methods: Facility points of contact completed a survey assessing their facility's use of 68 implementation strategies based on the Expert Recommendations for Implementing Change taxonomy. We collected respondent demographic information, facility-level characteristics, and case review completion rates (percentage of high-risk patients who received a case review). We used Kruskal-Wallis tests and negative binomial regression to assess strategy use and factors associated with case reviews. Results: Contacts at 89 of 140 facilities completed the survey (64%) and reported using a median of 23 (IQR 16-31) strategies. The median case review completion rate was 71% (IQR 48-95%). Neither the number or types of strategies nor completion rates differed by randomization arm. The most common strategies were using the STORM dashboard (97%), working with local opinion leaders (80%), and recruiting local partners (80%). Characteristics associated with case review completion rates included respondents being ≤ 35 years old (incidence rate ratio, IRR 1.35, 95% CI 1.09-1.67) and having < 5 years in their primary role (IRR 1.23; 95% CI 1.01-1.51), and facilities having more prior academic detailing around pain and opioid safety (IRR 1.40, 95% CI 1.12-1.75). Controlling for these characteristics, implementation strategies associated with higher completion rates included (1) monitoring and adjusting practices (adjusted IRR (AIRR) 1.40, 95% CI 1.11-1.77), (2) identifying adaptations while maintaining core components (AIRR 1.28, 95% CI 1.03-1.60), (3) conducting initial training (AIRR 1.16, 95% CI 1.02-1.50), and (4) regularly sharing lessons learned (AIRR 1.32, 95% CI 1.09-1.59). Conclusions: In this national evaluation of strategies used to implement case reviews of patients at high risk of opioid-related adverse events, point of contact age and tenure in the current role, prior pain-related academic detailing at the facility, and four specific implementation strategies were associated with case review completion rates, while randomization to additional centralized oversight was not. Trial registration: This project is registered at the ISRCTN Registry with number ISRCTN16012111. The trial was first registered on May 3, 2017.