Nowadays, teacher professionalization has been upgrading and the status, training and working conditions of teachers have received a great deal of interest for sustainable education. It is recognized that if teachers are equipped with adequate professional knowledge and personal practical knowledge, they will become active curriculum planners at schools--and will have the potentials to transform from "cook" to "chef" in teaching. Therefore, in-service training of teachers is one of the most effective ways of sharing professional experiences and a medium of sustainable education in the society. Based on the existing literature, the present study was conducted to investigate the preschool teachers' needs about in-service training courses (INSET) to suggest an effective INSET model based on their INSET needs assessment for sustainable education in a Turkish setting. A questionnaire consisting of fixed-response, open-ended and Likert-style questions was administered to preschool teachers (n = 133) currently working in Tokat, one of the vicinities of Turkey, to obtain information about their background characteristics and to determine their conceptions and needs for INSET for sustainable education. The study comprises two steps. As a first stage, socio-demographic structures of the INSET participants are analyzed in respect to different variables. In the second stage, the preferences of the INSET participants are analyzed regarding "before in-service training", "while in-service training" and "after in-service training" process.