Social media is becoming a major part of adolescents’ lives; however, excessive use could affect sleep quality and school performance. This research aimed to evaluate effects of social media on sleep quality and school performance among female high school students in Eastern Province, Saudi Arabia. In a cross–sectional study, 717 female high school students in Khobar and Jubail cities in Eastern province, Saudi Arabia, completed self–administrated questionnaires. The most used social media application was Snapchat (39.7%). Furthermore, 36.8% of participants used social media more than 6 hours/day, whereas only 2.4% used these applications less than 1 hour/day. For sleep duration, 37.2% of participants sleep for 5–6 hours. For school performance, half of the participants (50%) who use social media more than 6 hours/ day have failed. Social media use negatively impacts female high school students’ sleep quality and school performance. Strategies to raise awareness about these effects are needed.