The United States Department of Energy’s Wind and Water Power Technologies Office (WWPTO) funds a research portfolio aimed at strategically filling knowledge gaps in the understanding of environmental impacts of wave and tidal energy devices. This portfolio includes research, monitoring, and modelling efforts to assess the impacts of marine energy devices; work to advance environmental monitoring instrumentation; and initiatives to aggregate, analyse, and disseminate the results of marine energy environmental research occurring around the world. This paper explores the approach that the WWPTO has taken to addressing two potential issues of concern regarding possible effects of wave and tidal devices on marine life, with an emphasis on recent results from this portfolio of work and research funded since the publication of the Annex IV report. Specifically, it focuses on the potential effects of device-generated noise on local marine organism behaviour, movement, and habitat use patterns and the potential for blade strike from tidal devices to cause harm to marine animals. For both these interactions, a combination of WWPTO-funded laboratory research, field monitoring, and modelling efforts have helped bound the unders tanding of the level of potential environmental effects of these technologies. As a whole, the U.S. Department of Energy research program seeks to provide data which can be used to inform the consenting process for future projects, reduce environmental uncertainty, inform the design of effective monitoring regimes, and identify potential mitigation strategies where necessary.