The present study investigated the effects of teaching experience on teachers' self-efficacy in Kenyan secondary schools. The study used a sequential explanatory design and the Teacher Self-Efficacy Scale. This scale consisted of a total of 24 items with eight items measuring each of the three domains of teacher self-efficacy: student engagement, instructional strategies, and classroom management. The face and content validities of the modified Teacher Self-Efficacy Scale were ascertained by two experts in Educational Psychology from a Kenyan university. The sample size of the study comprised 327 teachers obtained using stratified random sampling technique. The quantitative data was analyzed using Multivariate Analysis of Variance (MANOVA) but qualitative data from interviews was analyzed thematically. The MANOVA results demonstrate that the effects of experience on teachers' self-efficacy was significant, Wilk's [lambda] (7, 319 = 0.945, p = 0.019). The article concludes that Kenyan Teachers' Service Commission should utilize experienced teachers as resource persons who are attached to several schools.