OBJECTIVE: The neuroelectrophysiology mechanisms of the connection between nonsuicidal self-injury (NSSI) and impairment of social decision-making function remain unknown. As the event-related potentials (ERPs) technique has been widely used in neurobiology research because of its advantage of high temporal resolution, we conducted this study to explore the ERPs of decision-making function among adolescents with NSSI. METHOD: This study was designed to compare patients with mood disorder plus NSSI with mood disorder patients without NSSI using a 2:1 ratio. Participants aged 12-18 years were recruited from the outpatient department of psychiatry at Nanfang Hospital. Sociodemographic and psychological data were collected. The Ultimatum Game, a task examining individuals' social decision-making, was conducted with the ERP technique to record participants' neural responses. The associations between ERPs characteristics and psychological factors were examined by using correlation analysis and regression analysis. RESULTS: In total, 90 participants were eligible, with 60 in the NSSI group and 30 in the non-NSSI group. N1 latency in the unfair condition was positively correlated with Difficulties in Emotion Regulation Scale scores (r = 0.257), whereas P2 latency in the fair condition was correlated with agreeableness personality (r = 0.250). Regression analysis revealed that N1 latency in the unfair condition was positively associated with NSSI (ORs ranged 1.07-1.10), whereas P2 latency in the fair condition was negatively associated (ORs ranged 0.95-0.97). CONCLUSION: NSSI patients tended to exhibit impairment in decision-making function including initial cognitive value judgment, attentional allocation, and working memory process. ERPs characteristics including N1 latency and P2 latency may be predictors of NSSI.