Abstract Despite the ubiquity of boredom and its aversive effects in educational contexts, it has received scant attention from second/foreign language (L2) researchers until very recently. This article reports on one of the first empirical attempts to explore boredom in L2 learning and its sources in Chinese tertiary-level EFL contexts through eliciting responses of 1,502 university students to open-ended questions and conducting 16 individual semi-structured interviews. The qualitative data analysis revealed that participants perceived wide-ranging learner-internal and learner-external factors as sources of their foreign language learning boredom: (1) task characteristics, (2) teaching and learning activities, (3) student factors, (4) course content, (5) classroom factors, (6) teacher factors, and (7) feeling unoccupied in the class. Moreover, open-ended responses showed greater prominence of the first three categories of factors than others, lending support to the central role of control-value appraisals in inducing boredom, and suggesting situation-sensitive nature of boredom. Additionally, the study revealed that multiple factors, both learner-internal and learner-external, can interact and jointly shape control-value appraisals, which suggests the congruence between the person-in-context perspective on SLA and the control-value theory, and the potential to integrate the two approaches to extend L2 emotion research.