The aim of this study is to find out the reasons of teachers’ dissent against school administration in secondary schools. The research was in survey model. The research population consisted of teachers working in the public secondary schools located in the city center of Mardin during the 2011-2012 academic year. Randomly selected 191 teachers composed the sample. The datum of the study were collected through a questionnaire of 23 items taken from “Dissent’s Reasons” section of “Scale of Organizational Dissent” which was developed by Özdemir (2010). The results derived from the data are as follows; (1) Teachers "occasionally" see the administrator's behaviors as something to dissent for. Teachers mostly dissent for “managers’ taking decision concerning teachers without consulting him/her" whereas teachers rarely dissent for “administrator's political disclosure.” (2) A significant difference is not determined between the mean of teachers’ opinions about the causes of organizational dissent for the variables of education level, seniority, gender, union membership, the number of teachers in the school