There is a growing consensus that teachers? social-emotional competence (T-SEC) is crucial for their own well-being and students? social and emotional learning (SEL). However, the literature lacks comprehensive, psychometrically sound, and practical measures of T-SEC. Moreover, the existing literature on T-SEC is predominantly grounded in Western countries, leaving this issue largely unexplored elsewhere. This study aims to introduce the Multidimensional Assessment of Teacher Social-Emotional Competence (MATSEC), measuring T-SEC across all five domains of the CASEL framework, with an additional domain focused on social awareness for equity and inclusion. This six-dimensional, self-reported scale was collaboratively developed by a team of East Asian researchers and practitioners through an iterative process of item generation and revisions based on expert reviews, cognitive interviews, and pilot testing. We evaluated various psychometric properties of this scale using data from school teachers in China and Korea (N?=?859). Exploratory and confirmatory factor analysis suggested a second-order factor structure involving a single overall T-SEC factor indicated by six sub-domain factors: (1) self-awareness, (2) emotion management, (3) social awareness for student well-being, (4) social awareness for equity and inclusion, (5) relationship skills, and (6) responsible decision-making. The overall scale and all subscales showed high internal consistency and concurrent validity, demonstrating significant correlations with teachers? various well-being outcomes, self-efficacy, and perceived school climate. Measurement invariance testing supported cross-country equivalence of the scale. We hope the MATSEC contributes to the emerging literature on T-SEC in East Asia, with the potential to be tested and applied in diverse educational contexts around the world.