Previous research has provided ample evidence for the processing advantage of formulaic sequences, leading researchers and teachers to argue for its facilitation of speech fluency. However, few studies have examined how the processing of formulaic sequences interacts with speaker proficiency and task difficulty; even fewer studies have investigated how formulaic sequences facilitate different dimensions of speech fluency. To address these gaps, this study examined the impact of formulaic sequences on speech fluency for both first and second language speakers (N = 269) across proficiency levels on elicited imitation tasks. Participants' speech fluency was measured on both rate and pausing features. Results from linear mixed-effects models reveal that formulaic sequences had a significant effect on the reduction of pauses, but not on speech rate. The effect on pausing was stronger in the processing of long sentences and on intermediate second language speakers. These results suggest that formulaic sequences have differential impacts on the rate and pausing dimensions of speech fluency, and the impacts are further conditioned by speaker proficiency and task difficulty. Findings of this study have both theoretical and pedagogical implications regarding the acquisition of formulaic sequences and the development of speech fluency.