Background Internet addiction is a global phenomenon that has been a topic of great interest to researchers, clinicians, teachers, parents, and community groups. The study aims in determination of the rate of problematic Internet use among a sample of Egyptian adolescent students, relations of problematic Internet use with socio-demographic data, risk factors, and comorbid psychiatric disorders. A sample of 248 Egyptian adolescent school students aged 11 to 18 years old were assessed using the Young’s Internet Addiction Test (IAT), Internet Gaming Disorder (IGD) Scale, Social Media Disorder (SMD) Scale, Youth Self-Report (YSR), and The Mini International Neuropsychiatric Interview for children and adolescents (Mini KID). Results Among the study sample, 42.3% of the students suffered from mild Internet addiction, 35.1% suffered from moderate Internet addiction, and 3.6% suffered from severe addiction. 31.5% were risky gamers and 10.5% were disordered gamers; 34.3% had problematic social media disorder and the highest observed psychiatric disorders were major depressive episodes 9.3%, generalized anxiety disorder 7.7%, alcohol dependence 4.4%, attention-deficit hyperactivity disorder 4.4%, social phobia 4%, and a higher percentage of psychiatric disorders among severe Internet addiction 88.9% and among moderate addiction 70.6%, disordered gamers 92.3%, problematic social media users 60%, and a higher mean of hours spent online per day of 6.8 h per day. Conclusions Problematic Internet use has a negative impact on Egyptian adolescent students in international schools in study sample and adds to the existing literature regarding the magnitude of Internet addiction and its relationship with different psychiatric disorders.