The purpose of the present study was to design and validate a scale for measuring the sources of English as a foreign language (EFL) teachers' apprehension (STAS). To design the scale, the data generated from a triangulated qualitative research (Goldast and Ghanizadeh forthcoming) was employed. The model incorporated four factors, including altitudinal, organizational, L2-related factors, and classroom management. A 35-item scale on a 5-point Likert scale was developed. The designed scale was distributed among 198 EFL teachers both from language institutes and schools. A confirmatory factor analysis (CFA) using Lisrel 8.5 statistical package was run. Implementing the modifications resulted in a refined version of the scale comprising 33 items and four factors (L2-related problems, attitudinal factors, classroom management, and organizational factors). It exhibited acceptable reliability and validity indices. To further validate STAS, its association with a highly related construct, i.e., teacher burnout was probed. A model was proposed containing teacher apprehension and teacher burnout. The model was tested via structural equation modeling (SEM). The results demonstrated that the model had a good fit with the empirical data. It was also found that EFL teachers' apprehension positively and significantly influenced teacher burnout.