Objective: This study aimed to classify types of fandom activities among adolescents and identify predictors influencing membership in each type, recognizing fandom as a psychosocial and developmental context for identity formation and social relationships. Methods: Data were drawn from the fifth wave of the 2018 Korean Children and Youth Panel Survey (KCYPS), including 837 second-year high school students (386 males, 46.15%). Latent Profile Analysis (LPA) using Mplus 8.3 was used to identify various types of fandom activities. Multinomial logistic regression was employed to examine the effects of psychological characteristics, smartphone dependency, and parenting styles on the classification types. Results: Three distinct fandom activity types emerged: (1) passive online engagement, (2) offline active participation, and (3) online participation-collecting hybrid. Gender, psychological traits (self-esteem, aggression, somatic symptoms, and cooperativeness), smartphone dependency subfactors (functional impairment, virtual life orientation, withdrawal, and introversion), and parenting styles (warmth, autonomy support, and structure) were significantly associated with the classification types. Conclusions: Fandom participation serves as a cultural adaptation strategy shaped by adolescents’ psychological traits and parenting environments, functioning as a psychosocial resource for identity formation and emotional development. The findings highlight the need for policies and practices that acknowledge fandom as a meaningful aspect of adolescents’ cultural and emotional lives.