Programming is increasingly introduced in secondary schools, both as a stand-alone subject or integrated into other subjects, leading to growing attention to the training of in-service teachers. Teachers need to learn both (a) how to program and (b) how to teach programming, often in the context of different disciplines. The paper explores the impact of a university-level training program offered to in-service teachers, with a focus on teachers’ self-efficacy in teaching programming. The paper reports the interviews with ten teachers after about one year they have completed the program. The results indicate that the training has improved teachers’ self-efficacy, and the impact is lasting in time. Also, some teachers expressed concerns about their skill level in programming, but this does not necessarily associate with lower self-efficacy in teaching programming. The paper presents the results from the study and some implications for the design of training of in-service programming teachers.