The objective of the present study was to explore the direct and indirect effects of academic boredom on foreign language (FL) proficiency in teaching English as a foreign language (EFL). As a prominent negative emotion, the detrimental effect of FL boredom on FL proficiency has been verified. However, the mediating mechanism between FL boredom and FL proficiency, especially the mediating effect of cognitive strategies, needs to be further explored. We recruited 505 Chinese EFL learners (236 female, 46.73%) from one secondary school using convenience sampling to verify the mediating role of elaboration strategies between FL boredom and FL proficiency. Structural equation modelling (SEM) and mediation analysis yielded two major findings. First, FL boredom was negatively correlated with FL proficiency. Second, after controlling for gender and age, FL boredom, mediated through elaboration strategies, influenced FL proficiency. Third, elaboration strategies partially mediated the relationship between FL boredom and proficiency. Implications and limitations are discussed.