Although a rich literature documents pre-literate children’s word learning success from shared storybook reading, a full synthesis of the factors which moderate these word learning effects has been largely neglected. This meta-analysis included 37 studies with 2,256 children, reflecting 104 effect sizes, investigating how the number of target words, tokens, story repetitions, reading styles and related factors moderate children’s word comprehension. Dialogic reading styles, tokens, the number of words tested and story repetition all moderated word learning effects. Children’s age, who read, number of target words and time between story and test were not moderators. These results provide information to guide researchers and educators alike to the factors with the greatest impact on improving word learning from shared storybook reading.