Social comparison on social media has received increasing attention, but most research has focused on one type of social comparison and its psycho-emotional implications. Little is known about how different types of social comparison influence youth's identity development. Drawing on the theories of identity processing styles and social comparison, we examined how two different forms of social comparison on social media related to three identity processing styles, which in turn predicted youth's global self-esteem and identity clarity. We surveyed 219 college freshmen (Mage = 18.29; 74% female) once in the Fall and once in the Spring. Social comparison of ability on social media was related to concurrent diffuse-avoidant identity processing style, which predicted lower identity clarity months later. In contrast, social comparison of opinion on social media did not influence college freshmen's global self-esteem and identity clarity through identity processing styles. The findings clarified the implications of online social comparison for youth's identity development.