Affective occupational commitment (AOC) during training is considered to prevent occupational turnover and positively influence later work-related outcomes and learning processes. However, little is known about AOC development in a training context. This study examines antecedents and consequences of AOC and its development during vocational education and training. Participants were 497 Swiss apprentices who took part in a longitudinal survey throughout their 3-year training program. The results of latent growth curve modeling showed a slight average decrease in AOC over time. Initial AOC was negatively related to occupational turnover intention and positively related to satisfaction with the apprenticeship. Perceived person-occupation fit and feelings of competence during in-company training were positively correlated with initial AOC. Change in AOC was the smallest when apprentices felt autonomous and larger when they felt competent. The results indicate how in-company training environments can be arranged that foster apprentices' AOC.