Professional development (PD) is increasingly used to improve early childhood educators' skills and knowledge in providing quality language and emergent literacy environments for children. However, the literature does not clearly indicate the extent to which such efforts reach their goals, or whether improvements in educator outcomes translate to learning gains for children. In the current synthesis, we conducted meta-analyses to evaluate the effects of language- and literacy-focused PD on process quality, structural quality, and educator knowledge as primary outcomes. Furthermore, we estimated effects for three child outcomes: receptive vocabulary, phonological awareness, and alphabet knowledge. PD produced a medium effect for process quality and a large effect for structural quality but no effect for educator knowledge. PD also produced a small to medium effect for phonological awareness and a small effect for alphabet knowledge, but these were not predicted by gains in educator outcomes. Although course and coaching intensity and duration were related to effect sizes, the total number of PD components was the strongest predictor of process quality. The results suggested that PD is a viable method of improving language and literacy processes and structures in preschools, but effects may need to be substantial if they are to translate into higher child outcomes. (author abstract)