Significant attention has been paid in the international literature to the effect of in-service training on the interaction skills of teachers in early childhood education and care. The growth of pre-service teachers during teacher education has received relatively little attention to date, however. In a mixed-methods longitudinal study, we monitored the development of interaction skills among a group of Dutch pre-service teachers with repeated measures for 3 years and structured interviews. The results of a linear mixed-effects model revealed an impressive growth of interaction skills during the pre-service training. The qualitative interview data revealed progress of pre-service teachers’ professional reflection on their interaction with young children. These outcomes show the effectiveness of pre-service training for the development of interaction skills and professional reflection in early childhood education and care. However, progress is relatively modest for instructional skills and this domain needs further investment in pre-service training.