Male partner resistance to family planning has been extensively cited as an obstacle to female contraceptive use in sub-Saharan Africa. Scholars emphasize that gender relations cause men to resist family planning and call for the incorporation of male gender norms into sexual and reproductive health programs, however a focus on exploring which specific norms of masculinity constrain men’s acceptance of family planning has been lacking. We conducted formative research to explore how men perceive family planning and how men, women, and providers perceive men’s role in family planning involvement. We found that many men appreciated family planning’s benefits but opposed their female partner’s contraceptive use because it undermined the ways they thought of themselves as men. Specifically, men spoke about how family planning use threatens masculine norms related to fertility, land, wealth, sexuality, and male household authority, which provokes anxiety about the inability to fulfill prevailing expectations of manhood. Nevertheless, both women and men felt that couples should make family planning decisions together and wanted men to be more involved. Drawing on our previous research, we plan to develop a theoretically informed and community-based intervention that strives to increase male acceptance of female partner family planning use by addressing men’s fears of a loss of masculinity. The intervention seeks to shift masculine norms associated with family planning resistance in the direction of greater family planning approval through family planning education, small group workshops, and community campaigns. The findings from this study will inform a future cluster randomized trial evaluating the impact of a masculinities-based approach to increase male family planning acceptance on women’s contraceptive prevalence.