Purpose: The primary aim of the study was to examine the association between early childhood practitioners' use of language facilitation strategies during interactive book reading of informational texts related to science and the language skills of preschool children with developmental language disorder (DLD). Method: Twenty-four practitioners (12 early childhood special education teachers and 12 speech-language pathologists) and 33 preschoolers with DLD participated. Practitioners received training and implemented an informational book-reading intervention for 19 weeks. Practitioners' use of language facilitation strategies (i.e., activating thinking by setting the informational text structure, asking target questions, asking inferential questions, and providing support) was coded using an observational tool. Children with DLD were assessed with a battery of language assessments at pre- and post-intervention. Results: Providing support significantly predicted the receptive academic vocabulary and receptive understanding of signal words of preschoolers with DLD. Practitioners asking target questions (direct questions related to targeted academic vocabulary and signal words) significantly predicted the receptive academic vocabulary of preschoolers with DLD. By contrast, these two types of language facilitation strategies were not related to expressive academic vocabulary or signal words. The other language facilitation strategies (i.e., activating thinking by setting the informational text structure and asking inferential questions) did not contribute to receptive or expressive academic vocabulary or signal words. Conclusion: Our findings suggest that asking direct questions and providing support may be effective mechanisms for supporting children's understanding of academic vocabulary and signal words during interactive book reading of informational texts.