Background: The relationship between social media (SM) use and disordered eating (DE) has not been adequately explored in young adolescents. Methods: Data from 996 Grade 7 and 8 adolescents (n = 534 girls; M age = 13.08) was investigated. DE cognitions (Eating Disorder Examination-Questionnaire [EDE-Q]), DE behaviors (Project Eating Among Teens), and SM use measures related to Facebook, Instagram, Snapchat, and Tumblr were completed. Results: DE behaviors were reported by 51.7% of girls and 45.0% of boys, with strict exercise and meal skipping the most common. A total of 75.4% of girls and 69.9% of boys had at least one SM account where Instagram was the most common, used by 68.1% of girls and 61.7% of boys. Global EDE-Q scores were significantly higher for girls and boys with each type of SM account, except for Facebook and Instagram for girls. A greater number of SM accounts was associated with higher DE scores for both cognitions and behaviors. Girls with Snapchat and Tumblr accounts and boys with Snapchat, Facebook and Instagram were significantly more likely to have both DE behaviors and over-evaluation of shape and weight in the clinical range. Greater daily time spent using Instagram was associated with significantly higher Global EDE-Q scores and DE behaviors for girls, while this pattern was also found for Snapchat usage and DE behaviors for girls. Conclusions: A clear pattern of association was found between SM usage and DE cognitions and behaviors with this exploratory study confirming that these relationships occur at younger-age than previously investigated.