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In L2 instruction and assessment, the application of research findings that adopt an integrative, psycholinguistic approach to explore the information-processing and speech-management facets of fluency seems necessary. This paper reports on a study that drew on Levelt’s (1989, 1999) speaking-specific model to probe the problem-solving mechanisms (PSMs) of fluent and nonfluent L2 speakers through a speaking-oriented questionnaire and a series of output-related retrospective interviews. The fluent and nonfluent L2 speakers were identified using a newly-developed analytic fluency scale and the task-related speech samples of 200 participants. The results revealed that the fluent L2 speakers employed cognitive, linguistic, and interactional PSMs more frequently and with greater facility than the nonfluent participants particularly to compensate for deficits in their conceptual repertoire, bridge communication gaps, and negotiate the intended meaning with their interlocutors. Specifically, they efficiently reshaped the preverbal plan to avoid failure, adeptly employed a variety of fillers and hesitation devices to maintain the communication flow, and attentively monitored the conversation. However, the nonfluent L2 speakers entirely abandoned or completely changed their original speech plan after running into deficiencies in their own outputs that made their speech utterly disjointed. Still at times, they struggled to self-correct their speech but failed due to deficient linguistic and interactional competence, which adversely led to more disfluencies. The findings suggest that further research into the cognitive, linguistic, and interactional processes underlying (non)fluent speakers’ use of PSMs can be useful in explaining speech disfluencies or learners’ differential L2 fluency.