The study investigated the influence of gender on teachers’ self-efficacy in public secondary schools of Kisumu County, Kenya. Bandura’s (1989) Social Cognitive Theory guided the study. The study employed the mixed methods approach within which a concurrent triangulation design was used. The target population was 1790 teachers in 143 public secondary schools from which a sample size of 327 teachers was drawn using stratified random sampling. Questionnaires and interview schedule were used to collect data. Piloting helped to clarify the test items, determine construct validity (r = 0.564 for items expected to have similar responses and r = -0.325 for items expected to have different responses) and establish internal reliability (Cronbach’s Į = 0.9976). Two experts in Educational Psychology established face validity of the data collection instruments. Qualitative data was transcribed verbatim and analyzed thematically while quantitative data was analyzed using descriptive statistics and Multivariate Analysis of Variance (MANOVA). The MANOVA results revealed that there was no statistically significant influence of gender on teachers’ self-efficacy, but the qualitative results revealed that gender had an influence on self-efficacy of teachers in co-educational and Boys’ schools. The study recommended that teacher counsellors be empowered to counsel female teachers on the challenges of teaching in co-educational and Boys’ schools.