The professionalization of teachers has become increasingly prevalent in recent years, leading to increased interest in the training, working conditions, and status of educators. This study addresses this interest by examining the in-service education and training (INSET) needs of English as a foreign language teachers in Türkiye. Despite recognizing the importance of in-service interventions for teacher development, educators often express concerns about the shortcomings of existing INSET programs. Key themes and patterns are identified through a meta-synthesis of ten relevant studies conducted between 2010-2021, including methodology, language skills, technology use, instructional practices, classroom environment, and material development. The analysis employs content and thematic analysis methods, enhancing the understanding of effective in-service training for English as a foreign language teachers and contributing to broader discussions on educators' training, working conditions, and status. The findings underscore the significance of designing INSET programs that address specific teacher needs, promote the practical application of new methods, and foster collaboration between the Ministry of National Education and teacher educators for successful implementation.