This paper aims to report on Chinese college students' emotions in English as a foreign language (EFL) speaking classrooms, including the trajectory of their emotions, and their perceived impacts of these emotions on their performances in class. Through conducting a case study among 12 Chinese college students and qualitatively analyzing the reflections and interview data collected over a semester, the present research, adopting the Positive Psychology perspective, reveals diverse emotions experienced by students in their EFL speaking classrooms. The emotions students felt were both complex and dynamic throughout the semester, and were found to interact with the changing internal and external factors, displaying a transition from the mixed emotions of excitement and anxiety to lower-intensity emotions (i.e., relaxation and boredom), and finally becoming inter-individually varied. As for the impacts of students' emotions, students believed that both positive and negative emotions were associated with their performances in class. The present study suggests that much attention should be paid to EFL college students' emotions in speaking classrooms both by themselves and by their teachers, and provides some possible sources of their emotions. In order to enhance students' psychological well-being and achieve better teaching effects, this study also recommends pedagogical practices that boost positive emotions and reduce negative emotions to be incorporated into EFL speaking classes.