Equipping elementary (i.e., grades K-5) teachers with adequate content and pedagogical knowledge to promote effective reading instruction based on the science of reading is a crucial piece of the reading education puzzle. We reviewed 20 empirical studies to examine the impact of teacher preparation and training programs on elementary teachers' knowledge of the science of reading, focusing on the foundational pillars of reading instruction, namely, phonological and phonemic awareness, phonics, and morphological awareness, as well as student outcomes in reading. We also identified program characteristics that promoted positive growth in teacher knowledge. Generally, findings support the effectiveness of training and preparation programs in increasing elementary teachers' knowledge of foundational constructs. Training in which teachers have the opportunity to apply their learned knowledge and skills under expert guidance produced the largest growth in teacher knowledge. Implications of findings are discussed.