The short form of the Experiences in Close Relationships Scale–Revised Child version (ECR-RC) is a promising self-report measure of anxious and avoidant attachment in Western adolescents, yet little is known about its psychometric properties across cultures. More importantly, little is known about attachment styles across cultures, child gender, and parental gender. The present study aims to address these limitations by studying the psychometric properties and measurement invariance of the ECR-RC in a sample of 1,232 Belgian and Vietnamese adolescents (45.9% boys, Mage = 12.3, SD = 1.20, range = 9.0–15.0; 61.36% Vietnamese adolescents). Results indicated that the factor structure of the mother-oriented ECR-RC was replicated across a Belgian and a Vietnamese sample and that the scale was invariant across both cultures and across gender and age. Vietnamese adolescents were more avoidantly and anxiously attached to their mothers compared to their Belgian counterparts. Boys were more avoidantly and anxiously attached compared to girls for the total sample. Considering two countries separately, boys were found to be more avoidantly attached, not anxiously attached compared to girls. Furthermore, with increasing age, more anxious and avoidant attachment was reported, except in Belgian adolescents where anxious and avoidant attachment did not differ over age. Focusing solely on the Vietnamese data, results revealed that the ECR-RC is a reliable measure to assess Vietnamese adolescents’ anxious and avoidant attachment to both parents. Vietnamese adolescents did not differ in their levels of anxious attachment toward both parents but showed higher avoidant attachment to fathers compared to mothers. (PsycInfo Database Record (c) 2022 APA, all rights reserved)