Narrative is fundamental to human thought, yet in many classrooms, expository texts are commonly used to support learning in content-based subjects, such as history. Given the importance of narrative, it might be harnessed as a powerful tool to support learning. This research compares the impact of narrative nonfiction (NNF) and expository text (ET) on the development and retention of conceptual understanding relating to World War I (WWI). In an experiment involving 78 participants (mean age = 10.2 years, standard deviation = 0.29), pupils were placed into one of two conditions: in one, information about WWI was conveyed primarily through NNF texts, and in the other, through ETs. Participants completed written pre-, post- and delayed post-assessments to assess development and retention of conceptual understanding. It was found that participants in the NNF condition showed greater chronological and causal thinking skills. In addition, participants in the NNF condition retained significantly more conceptual understanding at delayed post-assessments than those in the ET condition. Overall, these findings suggest that narrative texts have the potential to be powerful learning tools. Implications for how texts are selected and utilised to support learning in the primary, history classroom are discussed.