The aim of this study is to determine the effects of in-service education program (INSEP) that is developed for increasing the competences in the inclusive education of the pre-school education teachers (PSETs), on their knowledge level and self-efficacy perceptions, and on the satisfaction of the teachers with regard to the program. The pretest-posttest control group design was used in the study. The independent variable of the study is the INSEP that is applied to the control group. The dependent variables are the knowledge level and self-efficacy perception level of the teachers in the both group of inclusive education. The participants of the study consist of 35 pre-school teachers. The data of the study are collected through Information Form, Inclusive Education Information Test (IEIT), scale of "Teacher Efficacy for the Inclusion of Young Children with Disabilities (TEIYD) and INSEP Satisfaction Questionnaire. The analysis of the research data is performed by using SPSS 16.0 program. The data is received through IEIT and TEIYD, and analyzed through Dependent Sample t-test; and the satisfaction levels of the teachers are analyzed descriptively. In this study the INSEP is applied which aims to develop the competences of the PSETs' towards inclusion. As a result of the application, it is found that while there is no significant difference between the pre-test scores of the experimental group and control group (p>0.05); a significant difference is found between the post-test scores (p<0.05). Towards the effect of the applied INSEP on the self-efficacy perception of the teachers on inclusion, it is found that there is a significant difference between the post-test scores of the experimental and control groups (t(33)= 6.283, p=0.000). At the same time, it is determined that the teachers have positive view towards the applied INSEP.