In order to assess emotional competence in children, it is necessary to have psychometrically sound measures. To the best of our knowledge, there is no available tool to assess emotional competence in children from 3 to 5 years old that assesses the five emotional competences of the Bisquerra model and can be easily and quickly answered in the school environment. The objective of this study is to develop a measure, the Emotional Competence Assessment Questionnaire (ECAQ), and to provide evidence of its psychometric quality. Qualitative evidence was obtained from a systematic review, from two expert committees and from five discussion groups. On the other hand, quantitative validity and reliability evidence was obtained from a sample of 1088 students and other smaller subsamples. The results suggest that the ECAQ is a short and easy-to-use tool, easily understood by administrators. The quantitative results confirm a general factor of emotional competence adjusted for three specific factors. This factor has excellent internal consistency and test-retest reliability. The ECAQ has therefore been shown to be a promising tool for assessing emotional competence in children between 3 and 5 years of age.