This study was carried out to examine proportional reasoning problem solving processes of seventh grade students. This study was conducted with the explanatory sequential mixed method design. In this respect, firstly, quantitative data from 56 students were collected and analyzed. Then, qualitative data of the study was collected from six students selected according to their success and analyzed. The quantitative data of the study was consisted of a proportional reasoning skill test and analyzed using predictive statistics. The qualitative data of the study were collected through activity cards and the think-aloud protocol, and content analysis was applied to the collected qualitative data. The findings of the study showed that students were most successful at qualitative comparison. On the other hand, the least success was observed for quantitative comparison, and female students were found to be more successful in proportional reasoning problems.