Fluency in a second language (L2) involves a quintessentially cognitive processing system that operates quickly and effectively. The perceived importance of researching fluency through a psycholinguistic lens has motivated the related L2 research to resort to current cognitive speaking-specific models. This study, drawing on Levelt’s (1999a) psycholinguistic model, probed the deficiency sources (DSs) (non)fluent L2 speakers encounter in L2 communication and then surveyed the problem-solving mechanisms (PSMs) they happen to engage in to circumvent or mitigate the bottle-neck effects of the deficiencies. First, an analytic fluency rating scale was developed to assess the audio-recorded (monologic and dialogic) speech samples of a large number of L2 speakers and identify the fluent and nonfluent speakers. Two questionnaires and output-related retrospective interviews were employed to explore the (non)fluent L2 speakers’ DSs and PSMs. The MANOVA results and the interpretative analysis of retrospective data revealed that the nonfluent participants mainly suffered from resource deficits, processing time pressure, and perceived deficiencies in the interlocutor’s performance. Specifically, they felt adversely pressured by an onrush of competing plans or the absence of any to chart their minds, floundered on feeling incapable of configuring a viable syntactic structure for their intended meanings, were restrained groping for the right lemma to fit their notions, or faltered due to a daunting uncertainty of the phonological accuracy. Meanwhile, they resorted to ineffective oral-production strategies such as message abandonment and reduction, which resulted in disfluent speech. The fluent participants, however, did not suffer from these DSs and employed PSMs more consistently. They were able to dynamically reformulate the notions or the preverbal message, apply a revitalized encoding mechanism, use various stalling mechanisms, and negotiate meaning in order to monitor the articulation. The findings suggest that any attempt intended to improve or assess L2 fluency pivot on a psycholinguistic approach to L2 oral production.