This essay discusses the need for in-service training for teachers and the effectiveness of in-service training in school. In-service training act as a catalyst for teacher’s effectiveness. It is also a way of updating teachers’ skills and knowledge for improving teaching and learning which lead to better job performance. In-service training is important for teachers to face new challenges and changes in the education world. In-service training is also a fundamental aspect to improve teacher professionalism. The effectiveness of in-service training is important so that teachers can apply the knowledge acquired in teaching and learning. Few factors that contribute towards the effectiveness of in-service training are role of administrator, attitudes of teachers, training needs and strategies in conducting in-service training.