BACKGROUND Internet addiction is increasing among adolescents worldwide. There is a lack of research assessing internet addiction and factors contributing to it among adolescents in Jeddah city. The current study aimed to assess the rate of internet addiction among adolescents in Jeddah, Saudi Arabia, and the potential factors associated with it. METHODS A cross-sectional online survey, hosted by SurveyMonkey, was used to capture data on internet use from 462 adolescents aged 12-18 years between March and May 2022. Young's Internet Addiction Scale was used to assess the degree of internet addiction as perceived by adolescents. Multiple linear regression analysis was used to identify possible predictors of internet addiction among adolescents in Jeddah. RESULTS The mean age of the participants was 15.5 ± 1.9 years. The majority were females (75%) from public schools (63%), spent an average of six hours on the internet daily, owned smartphones (98%), accessed the internet via a smartphone (94%), and used the internet for socializing (82%). Internet addiction mean score was 39.20 ± 15.20 out of 100. More than two-thirds of the participants had mild to moderate levels of internet addiction (68%). Significant predictors contributing to internet addiction were using the internet for socialization and playing online games. The more hours spent on the internet daily, the more the internet addiction was (p ≤ 0.05). CONCLUSIONS The internet addiction rate is high among school adolescents in Jeddah. The majority of high school adolescents had mild to moderate levels of internet addiction. Interventional multidisciplinary programs are needed to mitigate the factors that influence internet addiction.