While many studies have demonstrated the relationship between musical rhythm and speech prosody, this has been rarely addressed in the context of second language (L2) acquisition. Here, we investigated whether musical rhythmic skills and the production of L2 speech prosody are predictive of one another. We tested both musical and linguistic rhythmic competences of 23 native French speakers of L2 English. Participants completed perception and production music and language tests. In the prosody production test, sentences containing trisyllabic words with either a prominence on the first or on the second syllable were heard and had to be reproduced. Participants were less accurate in reproducing penultimate accent placement. Moreover, the accuracy in reproducing phonologically disfavored stress patterns was best predicted by rhythm production abilities. Our results show, for the first time, that better reproduction of musical rhythmic sequences is predictive of a more successful realization of unfamiliar L2 prosody, specifically in terms of stress-accent placement.