Musical expertise has been shown to facilitate verbal working memory (WM) performance, but the findings lacked consistency. Given the overlapped auditory encoding process for language and music, there may be an association between one's native language background and the effects of musical expertise. In the present study, we investigate (1) the effects of musical expertise on verbal WM with different native language backgrounds and (2) the role of tone memory in the music-verbal WM link as a potential mechanism behind it. The data were collected as part of an experimenter-monitored online project, in which various memory functions were measured in musicians and nonmusicians speaking either tonal language (Mandarin Chinese) or nontonal language (Finnish). Results showed advantages of musical expertise on verbal WM only in the Finnish participants, but not in the Chinese participants. Tone sequence memory was identified as a mediator in the relationships between musical expertise and verbal WM. Our finding suggests that the beneficial effects of musical expertise on verbal WM could differ between different native language backgrounds. This potential benefit may come through the enhanced encoding of the auditory tone stimuli, which was shown to be possibly affected by language backgrounds. Therefore, we highlight the importance of considering language background in future studies when investigating the potential benefits of musical expertise and music interventions.