Adolescents are spending considerable time on social media, yet it is unclear whether motivations for social media use drive different forms of social media engagement, and their relationships with body satisfaction and well-being. This study tested a proposed model of the relationships between motivations for social media use, types of social media engagement and body satisfaction and well-being. Responses to an online survey from 1432 Australian adolescents (Mage = 13.45 years, SD = 1.14, range 11–17; 55.4% boys) were collected. Structural equational modelling indicates excellent model fit. Specifically, motivations for social media use (information sharing, passing time, escapism, social interaction, social capital and appearance feedback) were associated with engagement (intensity, photo-based use, active use, passive use and liking use) and revealed mixed associations with body satisfaction and well-being. The findings support the importance of considering motivations for social media use in future research.