The attention of researchers in the field of second language acquisition (SLA) has recently been drawn to boredom, recognized as one of the most prevalent and distressing emotions experienced by second and/or foreign language (L2) students. However, studies delving into boredom experienced by L2 teachers rather than learners are few and far between. This oversight is significant, considering that the emotions of both learners and teachers are bound to interact and feed into each other in classroom settings. In order to address this gap, the present research aimed to examine the factor structure and psychometric properties of the L2 Teacher Boredom Scale (L2TBS). The questionnaire was administered to 225 L2 teachers from different countries (e.g., Poland, Turkey, Hungary, Iran, USA). Data were subjected to exploratory factor analysis, confirmatory factor analysis and exploratory structural equation modeling (ESEM). The results identified the ESEM solution as the optimal model for measuring L2TBS. Five factors contributing to teacher boredom were identified: (F1) repetitiveness and monotony, (F2) inefficient communication, (F3) lack of satisfaction, (F4) lack of creativity, and (F5) lack of interest. The analysis also provided evidence for measurement invariance across gender, age, education and years of teaching experience.