This study investigates the impact of psychological stimuli on students' continuance intention to use massive open online courses (MOOCs), through the mediation effects of emotions under a stimulus-organism-response framework. Perceived competition, perceived risk, and curiosity are the psychological stimuli. Four emotions (happiness, interest, sadness, and anxiety), enjoyment, and stress are considered as the organism. Continuance intention to use MOOCs for learning is the response. To test the hypotheses empirically, 574 valid responses were collected from individuals who claimed that they had learning experience on the Chinese University MOOC. This is a well-known, official online learning platform supported by the Chinese Education Ministry and has the largest number of active MOOC users in China. The study employs partial least squares structural equation modeling to validate the research model. The results show that perceived competition has both positive and negative effects, perceived risk has no significant effect, curiosity only has a beneficial effect, and the four emotions play important mediation roles. This research unveils the internal effect mechanisms of psychological factors and emotions on continuance intention in the context of online learning.