The purpose of this study was to evaluate the reliability and validity of the Korean Behavior Assessment System for Children 3rd Edition Teacher Rating Scales--Child Form (K·BASC-3 TRS-C). We used the generalized partial credit model based on item response theory (IRT) to examine the internal validity of the scale's items and the latent trait in a sample of Korean children (n = 318). Findings based on IRT provided strong evidence for the discriminative characteristics of the items. Additionally, the results revealed that the difficulty and discrimination of most items were appropriate, and the reliability of the K·BASC-3 TRS-C was excellent. Concurrent validity was tested using the Teacher's Report Form for Ages 6-18 (TRF). Support for the external validity of subscale scores was found. A separate sample of 105 Korean children was used to examine the concurrent validity of a subset of the K·BASC-3 TRS-C subscales related to Anxiety, Hyperactivity, and Attention Problems demonstrated strong concurrent validity with TRF of related constructs. Other relevant findings, practical implications regarding the use of the K·BASC-3 TRS-C, and suggestions for future research are included in the discussion.