ABSTRACT: INTRODUCTION:Use of family planning (FP) is powerfully shaped by social and gender norms, including the perceived acceptability of FP and gender roles that limit women's autonomy and restrict communication and decision-making between men and women. This study evaluated an intervention that catalyzed ongoing community dialogues about gender and FP in Siaya county, Nyanza Province, Kenya. Specifically, we explored the changes in perceived acceptability of FP, gender norms and use of FP. METHODS:We used a mixed-method approach. Information on married men and women's socio-demographic characteristics, pregnancy intentions, gender-related beliefs, FP knowledge, attitudes, and use were collected during county-representative, cross-sectional household surveys at baseline (2009; n11 = 650 women; n12 = 305 men) and endline (2012; n21 = 617 women; n22 = 317 men); exposure to the intervention was measured at endline. We assessed changes in FP use at endline vs. baseline, and fitted multivariate logistic regression models for FP use to examine its association with intervention exposure and explore other predictors of use at endline. In-depth, qualitative interviews with 10 couples at endline further explored enablers and barriers to FP use. RESULTS:At baseline, 34.0% of women and 27.9% of men used a modern FP method compared to 51.2% and 52.2%, respectively, at endline (p<0.05). Exposure to FP dialogues was associated with 1.78 (95% CI: 1.20-2.63) times higher odds of using a modern FP method at endline for women, but this association was not significant for men. Women's use of modern FP was significantly associated with higher spousal communication, control over own cash earnings, and FP self-efficacy. Men who reported high approval of FP were significantly more likely to use modern FP if reporting high approval of FP and more equitable gender beliefs. FP dialogues addressed persistent myths and misconceptions, normalized FP discussions, and increased its acceptability. Public examples of couples making joint FP decisions legitimized communication and decision-making with spouses about FP especially for men; women described partner support as key enabler of FP use. CONCLUSIONS:Our evaluation demonstrates that an intervention that catalyzes open dialogue about gender and FP can shift social norms, enable more equitable couple communication and decision-making and, ultimately, increase use of FP.