Abstract Objective: WhatsApp (WA) is the most popular instant message application all over the world. Although communication has become easier and enjoyable with the help of this application, the overuse, and addiction of WA has become an important problem among adolescents. WhatsApp addiction is a part of problematic smartphone use (PSU). When we examined previous studies, we found that the samples were generally composed of young adults, but studies on adolescents who are at high risk for problematic Whatsapp use (PWU) were insufficient, and almost no studies were conducted in the clinical adolescent sample. In this study, we aimed to increase our knowledge about problematic Whatsapp use (PWU) and possible risk factors including fear of missing out (FoMO), PSU, and psychiatric symptoms among adolescents who applied to outpatient psychiatry clinics. Method: 197 adolescents (136 boys, 61 girls, age: 12-18 years) recruited the study. Problematic Mobile Phone Usage Scale (PMPUS), Bergen Whatsapp Addiction Scale, Brief Symptom Inventory, and Fear of Missing Out (FoMO) Scale were used. Results: We grouped the sample as PWU (Problematic WhatsApp use) and Normal Use group due to Bergen WA Addiction scale. PWU groups adolescents were significantly older than others (p=0.03), and had higher scores in all subscales of Brief Symptom Inventory (BSI), FoMO and PMPUS (for all scale scores p