Background: Implementation strategies used to enhance the implementation of interventions during efficacy and effectiveness studies are rarely reported. Tracking and reporting implementation strategies during these phases has potential to improve future research studies and real-world implementation. We present an exemplar of how this might be executed by specifying and reporting the implementation strategies that were used during a school-based efficacy trial, Project POWER, which tested a trauma-informed prevention program delivered by a university research team, community members, and school staff facilitators in 29 schools. Methods: Following the conclusion of the 4-year trial, core Project POWER research team members identified the implementation strategies that supported intervention delivery during the trial using an established taxonomy of school-based implementation strategies. The actors, actions, action targets, temporality, dose, and implementation outcomes were specified using established implementation strategies reporting guidelines. Results: The research team identified 37 implementation strategies that were used during the Project POWER trial. Most strategies fell within the categories of Train and Educate Stakeholders, Use Evaluative and Iterative Strategies, and Develop Stakeholder Interrelationships. Actors included members of the research team and partner schools. Strategies were used multiple times during the preparation and implementation phases. Action targets were most often characteristics of individuals, implementation process, and characteristics of the inner setting. Strategies predominantly targeted the implementation outcomes of fidelity, acceptability, feasibility, and adoption. Conclusions: This study provided evidence that implementation strategies are used and can be identified in efficacy research using a retrospective approach. Identifying and specifying implementation strategies used during the initial phases of the translational research pipeline can inform the implementation strategies that are carried forward, adapted, or discontinued in future trials and routine practice to improve implementation and effectiveness outcomes. [This paper was published in "Implementation Research and Practice" v2 p1-17 2021.]