The Yale-Brown Obsessive-Compulsive Scale Second Edition (Y-BOCS-II) is the gold-standard measure of obsessive-compulsive disorder (OCD) severity, yet no validated Indonesian version exists. This study evaluated the psychometric properties of the Indonesian Y-BOCS-II in 141 adult outpatients with OCD. The Y-BOCS-II demonstrated excellent internal consistency (KR-20 = 0.90 for Symptom Checklist and ω = 0.94 for Severity Scale), strong inter-rater reliability (ICC = 0.99), and high temporal stability over two weeks (ICC = 0.90). Confirmatory factor analyses revealed poor fit for both the original obsession/compulsion and alternative interference/control two-factor models. However, three-factor model (Time/Frequency, Resistance/Control, Distress/Interference) demonstrated acceptable fit (RMSEA = 0.09, CFI = 0.97, SRMR = 0.04). The scale demonstrated convergent validity with the Obsessive-Compulsive Inventory-Revised and Florida Obsessive-Compulsive Inventory Severity Scale, while maintaining discriminant validity from Patient Health Questionnaire - 9 and Generalized Anxiety Disorder - 7. These findings establish the Indonesian Y-BOCS-II as a reliable and valid measure for assessing OCD symptoms in Indonesian clinical settings and suggest presence of a three-factor conceptualization of OCD symptomatology. © 2025 Elsevier Inc.