The present articlerefers to the topic of inside-the-school conflicts among teachers of the same school. More specifically, itsmain purpose is to illustrate the secondary-education teachers’ opinions regarding the causes ofthe inside-the-school conflicts. The article showsaquantitative research employed in order to elaborate on this topic. An online questionnaire was completed by 126 secondary school teachers in the prefecture of Karditsa. The findings of the survey revealed that the teachers-participants consider the inside-the-school conflicts possible both among colleagues and between each individual and the head teacher. The most salient causes of those conflicts could be the time allocation within the timetable, the distribution of the teaching subjects, the assumption of responsibilities and duties, the negative atmosphere in the school and the managerial strategies followed. Extra emphasis was placed on the parameter of the financial crisis, which seemed to deteriorate the situation by reinforcing this type of conflicts. Both teachers and school principals can take into consideration the findings of the research in order to find out how they can be more effective at their work and achieve their professional goals.