The present study aimed to examine an effective mathematics teacher's qualifications from the perspectives of secondary school students. The study was a qualitative one carried out with the descriptive model. The study was carried out with 40 students from all the four class grades of a secondary school (10 students from each class grade) in Turkey in the academic year of 2017-2018. The participants were determined using the purposeful sampling method. As the data collection tool, semi-structured interview questions were used, and the interviews were audio-recorded to avoid any data loss. For the analysis of the data, first, the interviews were transcribed and then analysed using the content analysis method. The results revealed that according to the students' views, the qualifications of an effective mathematics teacher were grouped under four categories: "personal traits", "communication skills", "class management and teaching methods" and "measurement-evaluation". It was also seen that regardless of the school type they would choose for their high school education, all the students had an idea about the qualifications of a mathematics teacher and that it was not much easy to become an effective mathematics teacher. In addition, it was found that there were differences between the views of the 5th, 6th, 7th and 8th grade students with respect to their cognitive levels and needs. In line with the qualifications examined, various suggestions were put forward to increase the effectiveness of the mathematics teachers and of the process of mathematics teaching.