Formal pre-service training has been shown to be effective in building teacher self-efficacy beliefs. However, the impact of other, less formal, "teacher-like" pre-service experiences on the formation of efficacy beliefs has not previously been investigated. This study examines the associations between both formal and informal formative pre-service experiences and teacher self-efficacy. In addition, the effect of years of teaching experience on these associations was investigated. Three hundred fifteen teachers of general and Judaic studies in Jewish day schools in the USA responded to a survey about their formal pre-service experiences; informal experiences as youth advisors, camp counsellors and childcare supervisors; and two measures of teacher self-efficacy. Formal pre-service training and positive student-teaching experiences, as well as each of the three informal experiences, were found to be associated with positive teacher self-efficacy. Interestingly, formal and informal pre-service experiences appear to be associated with different aspects of teacher self-efficacy. Formal teacher training was most strongly associated with efficacy for instructional practices, while the positive informal experiences were most strongly associated with efficacy for student engagement. The potential impact of both formal and informal experiences did not appear to fade over time. On the contrary, for those variables where an interaction with years of teaching was detected, it was the efficacy beliefs of the most senior teachers that were most related to their pre-service experiences. These findings have important implications for the practice of both teacher trainers and those charged with recruiting and supporting teachers. (Contains 5 tables.)