The study examined adolescents' social functioning and its relationships with social Internet use, parental care, and peer influence. Data were collected from a sample of 496 adolescents (Male = 18.5%; Female = 81.5%, Mage = 15.9), and the idea that the relationship between parental care, peer influence. and social functioning of adolescents could be influenced by the mediating power of social internet use was tested. Consistent with this hypothesis, the results revealed positive and significant relationships between social functioning, social Internet use (r = .373, p < .01), parental care (r = .153, p < .05), and peer influence (r = .170, p < .01). Moreover, when social Internet use was introduced as a mediator to determine the strength of the relationships, the prediction of parental care on social functioning increased from 2.33% variance to 13.7%, while that of peer influence improved from 2.88% to 15.23%. In conclusion, findings established that social Internet use was a prominent factor in adolescents' developmental processes for optimal social functioning.