Self-esteem expresses the individual's approach to himself and affects the whole life in terms of mental health. Another important factor affecting self-esteem, which has a critical importance for the youth period, is social media. In the literature, there are many studies examining the relationship between social media use and self-esteem of young people. In this study, it was aimed to investigate the relationship between problematic social media use and self-esteem in university students and to test the mediating role of cognitive distortions in the relationship between these two variables. The sample of the study consisted of 239 young individuals, 197 (82.4%) female, and 42 (17.6%) males, with a mean age of 20.62 ± 1.92 years, studying at a private university. Participants were evaluated by administering the "Rosenberg Self-Esteem Scale (RSES)", "Social Media Disorder Scale (SMD-9)", and "Cognitive Distortions Scale (CDS)". The scales were administered via an online survey. Results revealed that there was a negative significant relationship between the problematic social media use levels of the participants and their self-esteem. In the model established to evaluate the mediating role of cognitive distortions in the relationship between problematic social media use and self-esteem levels, in the first step, it was found that problematic social media use directly predicted self-esteem negatively. In the second step, it was determined that the use of problematic social media negatively predicted the mediating variable cognitive distortions. In the third step, when cognitive distortions, which are mediator variables, are added to the model in the relationship between problematic social media use and self-esteem; it was determined that cognitive distortions played a partial mediating role in the sub-dimensions of "self-perception", "self-blame", "hopelessness" and "seeing life as dangerous", while the sub-dimensions of "helplessness" and "total scale scores" played a full mediator role. Our findings show that there is a negative relationship between the problematic social media use of young people and their self-esteem levels, and cognitive distortions play a mediating role in the relationship between both variables.