In this study, preliminary validation of the Caregiver Report in the Korean Psychoeducational Profile-Third Edition (K-PEP-3) is conducted to evaluate its clinical applicability for assessing young children with developmental concerns. A total of 159 children aged two to six years and eleven months and their caregivers participated in the study. Based on total scores from the Korean Childhood Autism Rating Scale-Second Edition (K-CARS-2), the sample was divided into an ASD-suspected group (n = 49) and a typically developing group (n = 110). Construct validity was examined through internal consistency and inter-subscale correlations, while criterion-related validity was assessed via associations with the K-CARS-2 and the Korean Vineland Adaptive Behavior Scales-Second Edition (K-Vineland-II). The results demonstrated that the K-PEP-3 Caregiver Report has acceptable internal consistency and significant positive correlations among subscales. All three subscales showed significant mean differences between the groups, supporting discriminant validity. Moderate positive correlations were observed with the K-Vineland-II tool, particularly in the Adaptive Behavior domain, while correlations with K-CARS-2 were generally low. An item-level analysis revealed that only a few items correlated significantly with K-CARS-2 within the ASD-suspected group. These findings suggest that the K-PEP-3 Caregiver Report can serve as a clinically meaningful supplement to professional assessments by reflecting children’s developmental characteristics in natural settings. The tool holds promise for use in early screening and individualized intervention planning