Students taking an early childhood education teacher training program in an university in Hong Kong (N = 509) responded to survey items, before or after practicum, concerning 2 self-efficacy variables (academic self-efficacy and career-specific self-efficacy) and 4 sources of teacher self-efficacy measured by the Self-Efficacy Inventory (SOSI). Confirmatory Factor Analysis (CFA) supported three sources: mastery and vicarious experiences, social persuasions, and physio-emotional arousal. Structural Equation Modeling (SEM) found that practicum had a positive association with mastery and vicarious experiences but near-zero associations with the other sources and the two self-efficacies. The findings called for a dire need to (1) cultivate cognitive competence in the junior year of teacher training programs, (2) review the conventional view on the values and functional role of practicum, and (3) maximize the potentials of the essential sources of self-efficacy during practicum that contribute to pre-service teacher’s academic and career-specific self-efficacy.