Negative and positive emotion regulation are important to psychological well-being. However, most individual-difference measures of emotion regulation focus primarily or exclusively on negative emotion regulation. In the present research, we sought to expand the widely used Difficulties in Emotion Regulation Scale (DERS) by including items assessing positive as well as negative emotion regulation. In Studies 1 and 2, we evaluated the new DERS-Expanded (DERS-X) with Chinese student and clinical samples. Findings demonstrate the DERS-X's robust factor structure, high internal consistency, good test-retest reliability of the test scores, and excellent convergent, discriminant, incremental, and predictive validity of the test score interpretations. The DERS-X consists of 11 first-order factors, where the six negative scales (Inattention, Unclarity, Nonacceptance, Ineffectiveness, Disinhibition, Disruption) and the five positive scales (Inattention, Nonacceptance, Ineffectiveness, Disinhibition, Disruption) contribute to two second-order factors: positive emotion dysregulation and negative emotion dysregulation. Additionally, the scores from the positive and negative emotion dysregulation scales can be combined to yield a total emotion dysregulation score. In Study 3, measurement invariance testing indicates the comparability of scores across genders but cautions against direct comparisons between clinical and student populations. This study establishes a link between DERS-X scores and depression and anxiety, highlighting its clinical implications as well as its potential for informing interventions. We conclude that the 33-item DERS-X may be a useful tool for assessing negative and positive emotion dysregulation in diverse settings. (PsycInfo Database Record (c) 2026 APA, all rights reserved).