Problematic Internet use has been assessed as a significant factor that negatively affects people's lives, and it is increasing to worrying levels. This study aims to investigate the differences in problematic Internet use based on depression, anxiety, and stress levels among late adolescent university students. The research group for the study is comprised of 543 university students, 378 females (69.6%) and 154 males (28.4%); 11 people's gender was undetermined (2%). The ages of students in the research group ranged from 17 to 28 with a mean age of 18.49 (SD = 1.06). The Problematic Internet Use Scale; Depression, Anxiety and Stress Scale, and a personal information form were used to collect data. The results show that problematic Internet use behaviors vary depending on depression, anxiety, and stress levels. As depression, anxiety, and stress levels increase, problematic Internet use increases. The results are discussed in light of the literature, and recommendations have been made for researchers and professionals working in the field of mental health.