Individual differences in children's language skills have been shown to stem in part from variations in the quantity and quality of parent speech input. However, most research focuses on mothers' input whereas less is known about the effects of variability in father input. In this article, we review the relation between parent input and child language development with a focus on low-income families, and review general findings about similarities and differences in mother and father speech. Within this review, we highlight conversation-eliciting speech, such as wh questions and clarification requests, which occur, on average, more frequently in father input than mother input. Conversation-eliciting speech is challenging for 2-year-old children and has been shown in research with mothers to relate to child vocabulary development. We then report a study examining whether fathers' use of conversation-eliciting speech relates to children's developing vocabulary skills at 24 months of age within a sample of low-income African American families. Understanding that speech input varies among fathers, and specific strengths that fathers bring to interactions with their young children can help speech-language pathologists develop and implement more effective interventions.