Mixed methods analyses of an online survey sample (n = 4942) of sexual and/or gender minority youth (SGMY) (age 14-29) explore the relationship between participation in online fandom communities and (1) socially-mediated identity milestones and (2) self-identification, comparing fandom participating SGMY versus non-fandom participating SGMY. Fandom participating youth were younger than their non-fandom participating peers, were more active online daily, and hit established identity milestones earlier and more rapidly. Fandom participating youth also identified with more complexity, using a broader variety of more non-traditional sexual identity and gender identity labels. Implications for research and practice are provided.