Fostering creativity among foreign language learners has consistently received attention from researchers. However, the positive psychological processes promoting creativity among third language (L3) learners remain understudied. Focusing specifically on L3 students, this study explored the associations between perseverance of effort (PE), subjective well-being (SWB), harmonious passion (HP), and creativity. Furthermore, the study investigated the possible mediating roles of SWB and HP in the relationship between PE and creativity. Participants were 430 Chinese college students who attended an obligatory L3 course. To analyze the data, the PROCESS macro for SPSS was used to perform a mediation analysis, and the results showed that (1) PE, SWB, and HP all positively related to creativity, (2) PE directly predicted creativity, (3) SWB and HP could serve as partial mediators in the relationship between PE and creativity, and (4) the direct impact of personal trait (i.e., PE) on creativity is smaller than the indirect impact of positive emotions (i.e., SWB and HP). These findings highlight the significance of PE, SWB, and HP in facilitating creativity among L3 students. Based on these findings, instructive suggestions for fostering creativity in L3 students are discussed.