Community-based partnerships are integral to mental health programming and research. However, there are limited published guidelines that apply the principles of community-based participatory research (CBPR), especially within the context of supporting vulnerable youth populations. This article demonstrates the application of the CBPR principles in cocreating an evaluation approach for a healthy relationships program for vulnerable youths with community partners. We present our research procedures and activities and highlight the importance of having a trauma-informed lens and flexibility with the research process and outcomes. We conclude the article by sharing our lessons learned and providing recommendations for future CBPR with vulnerable youths.