This study investigated whether self-identity mitigates the negative impact of upward social comparison on self-evaluation by reducing self-threat. A total of 243 young adults in South Korea (Mage = 25.32, range = 19-29; 131 females; 54%) completed online questionnaires assessing baseline self-esteem and three self-identity measures: Identification with Commitment, Consolidated Identity, and Self-Concept Clarity. Participants were then instructed to list three characteristics of a person they considered superior (upward social comparison condition) or three physical attributes of the first person they had met that day (control condition). Subsequently, they completed measures of self-threat and state self-esteem. Results showed that self-threat mediated the relation between upward social comparison and self-evaluation. Self-identity moderated this mediation, both with and without controlling for baseline self-esteem; however, this effect was observed only with Identification with Commitment among the three self-identity measures. These findings suggest that individuals with a clear sense of self-identity maintain positive self-evaluation when exposed to upward social comparison, as they feel less threatened by superior others. Reflecting on the differences among the three self-identity measures, we discuss potentially more effective identity development intervention strategies, particularly for young adults actively engaged in identity formation and social comparison.