This study investigates the dynamic connection between two emotional constructs, enjoyment and group-level emotion regulation (co- and socially-shared regulation), during one 21-week semester of online collaborative English language learning. The study involved 268 Chinese undergraduate English-major students who completed a series of English writing tasks in 88 online groups of three or four members. During their online collaboration, participants were invited to complete the enjoyment scale and the emotion regulation scale at three separate times at seven-week intervals. When analyzing the data, a latent growth curve (LGC) modeling approach was employed to examine the intercepts and slopes of participants’ scaled responses to questions regarding enjoyment, co-regulation, and socially-shared regulation and to analyze the covariance between them. The findings reveal that participants’ levels of enjoyment and group-level emotion regulation were generally high at the initial stage of their online collaboration and continued to increase toward the end of the semester. Furthermore, an increase in the level of their enjoyment was significantly and positively associated with an increase in the levels of both their co- and socially-shared regulation, with the relationship with socially-shared regulation during online collaborative learning being stronger. These findings will enable language teachers to develop strategies for supporting language learners’ emotion regulation in online contexts.