The well-documented disparities in availability, accessibility, and quality of behavioral health services suggest the need for innovative programs to address the needs of ethnic minority youth. The current study aimed to conduct a participatory, formative evaluation of "Working on Womanhood" (WOW), a community-developed, multifaceted, school-based intervention serving primarily ethnic minority girls living in underserved urban communities. Specifically, the current study aimed to examine the feasibility, acceptability, and initial promise of WOW using community-based participatory research (CBPR) and represented the third phase of a community-academic partnership. Qualitative and quantitative data were collected from 960 WOW participants in 21 urban public schools, as well as WOW counselors, parents, and school staff over the course of one academic year. Results demonstrated evidence of acceptability of WOW and noteworthy improvements for WOW participants in targeted outcomes, including mental health, emotion regulation, and academic engagement. Findings also indicated several challenges to implementation feasibility and acceptability, including screening and enrollment processes and curriculum length. Additionally, we discuss how, consistent with participatory and formative research, findings were used by program implementers to inform program improvements, including modifications to screening processes, timelines, curriculum, and trainings - all in preparation for a rigorous effectiveness evaluation.