The main objective of this study is to identify the ideas of the teachers and administrators about the relation between the unionization of teachers and decision-making and communication processes among school management processes. Research data were obtained from the teachers and school administrators who work in primary, secondary, and high state schools within the borders of Battalgazi district of Malatya province during 2015-2016 and 2016-2017 academic years. The research is twodimensional, qualitative data source was obtained through "interview" technique and the quantitative data source was obtained through "Scale for the Effect of Unionization on School Management Processes-SEUSM", which was developed by the researcher. While analyzing the research data, content analysis was used for the qualitative dimension, and initially construct validity of SEUSM exploratory factor analysis and confirmatory factor analysis were used for the quantitative aspect and Cronbach Alpha reliability and item-total correlations, descriptive statistical analysis (t-test, standard deviation, frequency, arithmetic average) were used for reliability study. As a result of the study, the opinions of the teachers about the effect of their membership with the unions acting in the branch of education, training, and scientific services on decision-making and communication process at school do not differ statistically based on the variables that are gender, seniority, the type of the school where they work and the union. However, it was stated that if the school manager and the teachers, who are a member of the union with the highest number of members, are the members of the same union, cooperation and helping each other come to the forefront in decision-making and that fractions (groups) are it emerged against the members of other unions in the environments in which the number of the teachers, who are members of the same union is high. The administrators stated that they felt this much more in cases if they are not from the same union with the teachers, who are the members of the union with the highest number of members.