Shared book reading is an important context for children’s vocabulary development. Yet, the process by which word learning is influenced by the characteristics of both the learning material and the learner remains poorly understood – particularly in relation to contemporary digital literacy practice. We examined the effects of book format (print vs. digital) and individual differences in prior vocabulary knowledge and executive functions on children’s word learning. English-speaking caregivers and their 4- to 5-year-olds took part in this study (N = 99; child’s Mage = 57.5 months; 57.6 % girls). In a cross-sectional, within-subjects design, dyads read one of two custom storybooks in print, and the other in digital format, with order of book and format presentation counterbalanced across participants. Word learning was assessed with tests of production, definition, and comprehension. There was no evidence of a main effect of book format across word learning measures, however, several child characteristics influenced word learning. Prior vocabulary knowledge predicted performance on all word learning measures, boys were more accurate than girls in tests of definition and comprehension, and executive functions significantly predicted performance in the definition test. In addition, there was a significant cross-over interaction between book format and executive functions for the comprehension test scores. In the digital book condition only, higher comprehension test scores were obtained by children who scored more highly on the measures of executive functions. Overall, these findings underscore the importance of considering individual differences and multiple outcomes when studying learning from different media.