Smartphone addiction has emerged as a major concern among children over the past few years and incredibly increase with the outbreak of COVID-19, making a greater threat to their physical and mental health. This study aimed to assess the prevalence of smartphone addiction and its relation to bullying victimization, sleep problems, and depression among children. Sample: a total of 300 children (102 boys and 198 girls), 9-14 years old participated in the study. Setting: This study was conducted at two schools (Salka primary school, and 'Salka' preparatory school) in Salka village, Shpin Elkom city, Menoufia Governorate, Egypt. Tools: Four tools were used for data collection. Tool 1 consists of two parts. Part one was sociodemographic data questionnaire and part two was Smartphone Addiction Inventory Scale. Tool two: Children’s Sleep Habits Questionnaire (CSHQ). Tool three: School Bullying/Victimization Scale. Tool four: Center for Epidemiologic Studies Depression Scale (CES-D). Results: According to the cut-off level on the smartphone addiction, sleep quality, depression, and bullying scales, of the 300 children, 209(69.67) were addicted to smartphones and 246 (82%) have poor sleep quality, 264 (88%) were depressed and 249 (84.41%) were bullied.