This study investigated Korean adolescents behavioral and neural responses to the semantic and syntactic anomalies inKorean compared with adults, focusing on the case marking mismatches. EEG data were collected from 16 Korean ado-lescents (12 males, aged 12-14 years) using a picture sentence verification task regarding (A) verbal mismatch [AGENT-NOM + Verb/*Verb] (e.g., - /*; Brother-ka catches/*bites) and (B) case marker mismatch [AGENT-NOM/*ACC + Verb](e.g., -/*- ; Brother-ka/*-lul catches). The behavioral results showed 95% accuracy of their judgment regardless of condi-tions.The ERP data revealed differences between the conditions: N400 was elicited for verbal mismatches as well as forcase marker mismatches. The results are different from data collected from Korean adults, where the syntactic anomalieselicited early negativity at the case marker in addition to the N400 at the verb. The different ERP responses between adultsand adolescents to the syntactic anomalies provide evidence for the continuous development of human brains.