Reflective thinking is an important aspect that should be developed by students because they often face problems which are not immediately able to be solved, while students are required to be able to resolve them. Students need to have the awareness to think, predict, and seek simple formulas, and then prove the truth. This research aims to describe the processes of reflective thinking of tenth-grade students in solving mathematical problems. This research is qualitative in nature. Subjects are students in the tenth-grade of MAN (Madrasah Aliyah Negeri) Ngawi in the second semester of the 2015/2016 academic year. Data were collected using task-based interviews and are analysed using Miles and Huberman's technique (1994) consisting of three activities; data reduction, data presentation, and conclusion. Results showed that students with high and average initial mathematical ability were already able to apply reflective thinking processes in solving mathematical problems. The results of this research indicated that students with low initial capability in Mathematics did not use reflective thinking processes for problem solving. Therefore, teachers needed to provide scaffolding to them so that they could apply reflective thinking in solving mathematical problems.