The purpose of this study was to identify how secondary education students define the concept of justice, based on which criteria they define their experiences as just/unjust, what they see as the source of injustice, how they feel and how they behave when they face injustice. This study was designed as a qualitative research study. Open-ended questions were asked to the students and they were asked to give detailed answers. Descriptive analysis was used in analysing the collected data. The study group consisted of students studying at 9th, 10th, 11th and 12th grades in different types of high schools (Anatolian High School, Vocational School for Girls, Science High School). A total number of 268 high school students participated in the study. We used convenience sampling to choose the study group. The results of the study indicated that students defined the concept of justice with the "equality, equity non-discrimination, respect, rights and freedoms, conscience, rights, deciding the right, being fair and needs" concepts. The students see grades, school rules and non-communication they experience with their teachers and principals as unjust, so they point the school principals as the source of injustice. Besides, the students indicated that they had negative feelings when they experienced something that is not just but preferred to stay silent.