One of the important developmental tasks in adolescence and emerging adulthood is the questioning of identity issues, with body image being a prominent concern. In the age of modern technology, many processes of social comparison take place on social media, which serve as an ideal platform for comparison with others. The aim of this study was to examine the effects of identity dimensions, social media use, and social media social comparison, on different domains of body image satisfaction (i.e., appearance, weight, and attribution). An online survey was conducted with 354 young people in Croatia (Mean age = 18.49, SD = 1.44; Women/girls = 78.9%). The results revealed that each of the body image domains had a different pattern of association with identity dimensions and social media social comparison. The contribution of identity dimensions was more important for evaluation attributed to others about one’s body appearance, whereas social media use and social comparison were more crucial for thoughts and feelings about appearance and weight satisfaction. Higher identity commitment and exploration were related to more positive thoughts about how others evaluate one’s appearance, regardless of social comparison. On the other hand, social media use and social media social comparison were associated with lower satisfaction with appearance and weight.