Scholars debate whether musical and linguistic abilities are associated or independent. In the present study, we examined whether musical rhythm skills predict receptive grammar proficiency in childhood. In Experiment 1, 7- to 17-year-old children (N = 68) were tested on their grammar and rhythm abilities. In the grammar-comprehension task, children heard short sentences with subject-relative (e.g., "Boys 'that help girls' are nice") or object-relative (e.g., "Boys 'that girls help' are nice") clauses, and determined the gender of the individual performing the action. In the rhythm-discrimination test, children heard two short rhythmic sequences on each trial and decided if they were the same or different. Children with better performance on the rhythm task exhibited higher scores on the grammar test, even after holding constant age, gender, music training, and maternal education. In Experiment 2, we replicated this finding with another group of same-age children (N = 96) while further controlling for working memory. Our data reveal, for the first time, an association between receptive grammar and rhythm perception in typically developing children. This finding is consistent with the view that music and language share neural resources for rule-based temporal processing.