We explored the relationships between L2 utterance fluency and cognitive fluency in monologic and dialogic tasks. The study involved 136 Chinese university-level English learners. Utterance fluency was measured through speed, breakdown, and repair fluency aspects. Cognitive fluency was indicated by L2 lexical and syntactic processing efficiency measures. Stepwise regression models, including metrics of L2-specific cognitive fluency, L2 knowledge, and L1 utterance fluency as predictors, targeted L2 utterance fluency as the dependent variable. We found that L2 cognitive fluency predicted limited variance in utterance fluency, with its influence more evident in monologues. L2 lexical processing efficiency paralleled syntactic processing efficiency’s importance in the monologic task but surpassed it in dialogues. Moreover, L2 processing speed had a more significant impact on utterance fluency than processing stability across both contexts. We suggest that cognitive fluency is not the sole determinant of utterance fluency; L2 knowledge and L1 utterance fluency play non-negligible roles.
