The Land-Grant University Cooperative Extension (herein: Extension) system has been an underutilized resource for physical activity programming. With the recent addition of physical activity as a focus of Extension work, efforts are needed improve dissemination and implementation of evidence-based physical activity interventions. Improving implementation requires overcoming limitations including institutional support and perceptions of Extension health educators who could develop, deliver, and evaluate these programs. A participatory approach that includes input at all delivery levels (program participants, delivery agents, and administrators) can aid implementation through considering program acceptability, appropriateness, and feasibility from the beginning. This dissertation includes three manuscripts that explore the Extension's role in promoting physical activity in older adults, both in the United States and abroad. Manuscript 1 detailed a systematic review of community-based older adult physical activity programs that was conducted in order to determine the characteristics of effective older adult physical activity programs and the extent to which programs implemented in Extension systems nationwide employ these characteristics. The results indicated notable differences between peer-reviewed literature and Extension programs as well as presented an opportunity for Extension programs to more effectively use evidence-based program characteristics, including behavioral theories and group dynamics. The results also suggested that Extension programs could more effectively report their findings through peer-reviewed sources so that effective programs can be disseminated to reach a broader population. Manuscript 2 was an exploratory study conducted as a first step in bringing older adult physical activity programming to Ghana through Extension. Results of the mixed-methods study suggested that older adults in Ghana have mostly positive perceptions of physical activity and would be receptive to an in-person physical activity program. In particular, without specific prompting on principles of group dynamics, across all focus groups, participants mentioned aspects of groupness ranging from the need for accountability to the enjoyment of exercising with others. The results also indicated a need for education on Ministry of Health physical activity recommendations and how to meet them. These findings can be used as the first step to adapting and delivering an evidence-based intervention in Ghana through an integrated research-practice partnership. This approach includes community-level decision making to ensure the resultant program is a good fit in the intended delivery system. Manuscript 3 detailed the translation of an evidence-based older adult physical activity program to an Extension system in a rural state (population 585,501). Results suggested that Extension health educators have overall positive perceptions of physical activity programming, but they experience barriers in delivering these programs. While the program has the potential to reach a representative sample of the population, the adoption rate among Extension health educators was low, and system-wide changes may be needed to improve physical activity program adoption rates among educators. Overall, results of the three manuscripts provided evidence and recommendations for Extension professionals to improve physical activity program implementation through using evidence-based interventions and characteristics, considering perceptions of end users prior to program implementation, and considering system-level changes that promote physical activity program adoption.