["TESOL Quarterly, EarlyView. ", "\nAbstract\nThis classroom study explored the effects of vocabulary support on collocation learning and affective responses in task‐based language teaching (TBLT) among English‐as‐a‐foreign‐language (EFL) learners at a Japanese university. For this purpose, 68 EFL learners completed two interactive information‐gap tasks under either vocabulary‐support or task‐only condition, in which the first group received a list of collocations, whereas the second did not. Collocation learning was assessed through a pretest and a posttest, and learners' affective responses to the tasks were measured using a posttask questionnaire. Results revealed that the vocabulary‐support group outperformed the task‐only group in collocation learning. However, the task‐only group demonstrated higher positive psychological states, including enjoyment, pride, and perceived partners' collaborativeness, as well as lower boredom. Higher‐proficiency learners in the task‐only group exhibited stronger pride than those in the vocabulary‐support group. Furthermore, collocation learning gains were correlated with enjoyment, boredom, and perceived collaborativeness in the vocabulary‐support condition only. These findings underscore the potential link between emotions and lexical learning, suggesting that vocabulary support improves collocation learning but may diminish positive affect during tasks. Thus, further research on the relationship between emotion and cognition in TBLT is needed to seek an optimal balance between linguistic support and affective dimensions.\n"]