In today’s world, where change is inevitable, in-service training is becoming more and more important in ensuring professional development. Teachers maintain their professional development through in-service training. Vocational training sessions held in primary schools are an educational requirement as well as being a legal obligation. The aim of this study is to evaluate the efficacy of the in-service training sessions organized for teachers in primary schools in June and September, and where appropriate, make recommendations. The views of primary and secondary school teachers on in-service training sessions held within the framework of in-service training activities were obtained via semi-structured interview form. 96 teachers working in downtown Bartın and its counties participated in the study. The study was carried out during in-service training sessions in June, and it aims to determine the said in-service training sessions’ contribution to and efficacy for the teachers’ professional development. The study concludes that teachers do not play a role in the needs analysis process carried out within the framework of in-service training activities, in-service training has a theoretical contribution to the professional development of teachers, methods and techniques used in the in-service training activities are not suitable, and the evaluation process is insufficient.