Given the increasing use of social networks among children and adolescents, this systematic review aims to assess the impact of social media use (SMU) on teenage mental health. Google Scholar, PubMed, Web of Science, Science Direct, and Cochrane Library were searched. Study articles were screened by title and abstract using Rayyan QCRI, then implemented a full-text assessment. A total of fifteen studies with 327134 patients were included. The number of social media accounts adolescents have and how frequently they check them are related to loneliness, FOMO, impulsivity, hyperactivity, and anxiety. Adolescents frequently had problematic SMU, which was indicative of poor mental health, worsened depressive symptoms, and was related to low self-esteem. SMU seems to have a negative effect on teenage mental health for both genders, as both genders reported higher levels of loneliness and depressive symptoms.