Our study investigated the role of creativity in second language (L2) speech production using a picture narrative and an open-ended argumentative task administered to 60 Japanese-speaking learners of English. Following recent findings in the field of psychology, the participants' creativity was assessed in terms of cognitive dimensions (divergent thinking fluency, convergent thinking) and a personality dimension (openness to experience). Participants' speaking performance was analyzed using a set of complexity, accuracy, fluency and discourse measures. The results of hierarchical multiple regression analyses showed that both divergent thinking fluency and convergent thinking played a role in the cohesion of speech (indexed by the frequency of connectives) in both speaking tasks, while only in the argumentative task did divergent thinking fluency contribute to an increase in the amount of information (indexed by the total number of words produced). Meanwhile, openness to experience was found to enhance syntactic and lexical complexity only in the picture narrative task. These findings suggest that speakers' creativity is linked to syntactic and lexical sophistication and discourse aspects of L2 oral performance, all of which are related to conceptualization processes in L2 speech production.