The aim of the current study is to develop and validate an instrument to measure the four sources of teacher efficacy among Chinese primary school teachers. A 26-item Sources of Teacher Efficacy Questionnaire (STEQ) was proposed with four subscales: mastery experience, vicarious experience, social persuasion, and physiological arousal. The results supported the hypothesized four-factor structure of the STEQ. Scores from all the four factors of the STEQ had strong significant correlations with the Teachers' Sense of Efficacy Scale (TSES), which showed the criterion-related validity of the STEQ. Further, scores of all four sources significantly predicted teacher efficacy scores, among which social persuasion was the strongest predictor. This study contributes to the self-efficacy literature by providing researchers with an instrument for examining the various facets of teacher efficacy. The findings can inform school principals and teacher educators, enabling them to facilitate a school culture and teaching environment that cultivates a greater sense of teacher efficacy and, in turn, better teaching performance.