Background (Background, Rationale, Prior Research, and/or Theory): College students are at risk for unhealthy dietary behaviors, increased stress levels, and decreased physical activity. Development of healthy lifestyle patterns in adolescence is correlated with reduced risk of obesity later in life. Objective: To describe the process of using Community Based Participatory Research (CBPR) to develop and pilot test a health promotion intervention designed to prevent unwanted weight gain among “at risk” first-year college students. Study Design, Setting, Participants, Intervention: CBPR partners, including faculty researchers (n = 31), student researchers (n = 154), Extension professionals (n = 11), and college students (n = 83), from 12 universities identified program objectives and behaviors to target for health promotion on college campuses. Partners used identified objectives and behaviors to develop a social marketing intervention and a pilot/feasibility test of the intervention that was delivered over 24 weeks at four intervention universities, while no change occurred at four control universities. During and following implementation, partners and a student-led multistate social marketing committee adjusted the intervention and compiled materials into a comprehensive toolkit. Outcome Measures and Analysis: The pilot test was assessed in formative and process evaluations for key stakeholder acceptability and feasibility through weekly collaborative partner meetings, tracking social marketing engagement, weekly reports from campus coordinators (event attendance, supplies/cost, and perspectives of strength, weaknesses and modifications needed), toolkit evaluation surveys completed by student researchers and college students (n = 10), and town hall campus meetings. Results: An acceptable and feasible comprehensive toolkit was the final output from all data collected and analyzed, which was based on the elements of diet, physical activity, and stress management. The toolkit provides a systematic approach to assessing student health behavior and priorities, obectively measuring campus healthfulness, providing health promotion activities, using social marketing to promote health, and advocating for environmental change. Conclusions and Implications: CBPR can be used successfully to develop an obesity prevention intervention on college campuses. The effectiveness of the CBPR developed intervention to prevent unwanted weight gain needs to be evaluated in a randomized controlled trial. Funding: NIFA.