Background: Prominent theories of reading make the prediction that individual differences in children's word learning capacity determine the pace of their acquisition of reading skill. Despite the developmental nature of some of these theories, most empirical research to date has explored the relation between word learning capacity and reading at a single time point. The present study extends this research base by investigating whether earlier learning of the spelling and meaning of words is associated with later core aspects of reading: orthographic representations, word reading and reading comprehension. Methods: Participants were 120 English-speaking children followed longitudinally from Grade 3 to Grade 4 (i.e., from 8 to 9 years of age on average). At Grade 3, children read stories containing new words and answered questions about the spelling and meaning of these new words, evaluating orthographic and semantic learning, respectively. Children also completed outcome measures of orthographic representations (with a choice task targeting the spelling of existing words), word reading and reading comprehension (with standardised tasks) at Grades 3 and 4. We conducted regression analyses controlling for age, nonverbal reasoning, working memory, vocabulary and phonological awareness. Results: We found that each of orthographic and semantic learning predicted gains in orthographic representations from Grade 3 to Grade 4. Furthermore, orthographic learning at Grade 3 predicted word reading at Grade 4, while semantic learning at Grade 3 predicted reading comprehension at Grade 4. Conclusions: These longitudinal associations between orthographic and semantic learning and core aspects of reading strengthen the evidence in support of the hypothesis that children's word learning capacity plays a key role in reading development.