This is a study of early picture book comprehension, its determinants and later development through primary school. More specifically, picture book comprehension was analyzed longitudinally from age 5 to age 9, delineating the unique contributions of vocabulary, metacognitive knowledge and task orientation to the initial level as well as to the growth of comprehension. A total of 90 Finnish-speaking children participated in the study. The children’s narrative picture book comprehension was assessed at age 5, age 6 and age 9. Vocabulary, metacognitive knowledge and task orientation were evaluated at age 5. Latent growth curve modeling showed a pattern of decreasing achievement gaps in narrative picture book comprehension. Vocabulary and metacognitive knowledge uniquely contributed to the concurrent level of narrative picture book comprehension. The results further showed that metacognitive knowledge and task orientation were positive and statistically significant predictors of the growth of picture book comprehension over and above the initial level of narrative picture book comprehension. These findings add to our knowledge about the development of inter-individual differences in narrative picture book comprehension and the roles of vocabulary, metacognitive knowledge and task orientation in it. They also suggest a novel way to assess the narrative comprehension potential among students with compromised working memory or decoding ability.