Purpose: Stuttering is a neurodevelopmental disorder that disrupts the timing and rhythmic flow of speech production. There is growing evidence indicating that abnormal interactions between the auditory and motor cortices contribute to the development of stuttering. The present study investigated speech auditory-motor synchronization in stuttering adults and the influential factors behind it as compared to individuals without stuttering. Method: Sixteen Mandarin-speaking adults with stuttering and 19 fluent controls, who were matched for age, gender, and years of musical training, participated in the current study. Their ability to synchronize vocal speech production with accelerating auditory sequences was assessed using the spontaneous speech-to-speech synchronization test (SSS test). Additionally, all participants conducted a series of standardized behavioral tests to evaluate their musicality and executive functions. Results: Stutterers achieved significantly lower phase locking values in the SSS test compared to nonstuttering controls, indicating a potential rhythmic processing deficit in developmental stuttering. Moreover, the strength of speech auditory-motor synchronization in stutterers was significantly associated with their performance in tasks such as digit span and nonword repetition. This finding further emphasizes the strong link between rhythmic processing and working memory. Conclusions: This study provides compelling evidence for the speech rhythmic deficit in individuals with stuttering by incorporating auditory-motor processes. It would offer valuable insights into the intricate relationship between language and the brain and shed light on the potential benefits of cognitive training for speech intervention in individuals with stuttering difficulties.