Social media has created a new social landscape for adolescents. Knowledge is needed on how this landscape shapes adolescents' social skills and time spent with friends, as these outcomes are important to mental health and psychosocial functioning. Using five waves of biennially collected data from a birth cohort assessed throughout age 10–18 years (n = 812), we found that increased social media use predicted more time with friends offline but was unrelated to future changes in social skills. Age and sex did not moderate these associations but increased social media use predicted declined social skills among those high in social anxiety symptoms. The findings suggest that social media use may neither harm nor benefit the development of social skills and may promote, rather than displace, offline interaction with friends during adolescence. However, increased social media use may pose a risk for reduced social skills in socially anxious individuals.