Flipped learning has become a popular approach in different educational fields, including foreign language learning. The present study investigated the impact of teaching vocabularies via flipped classrooms on Iranian EFL learners’ foreign language anxiety (FLA). A total of 90 pre-intermediate Iranian EFL learners participated in this study. One class was randomly assigned to the flipped group as the experimental one (N=45) and the other was non-flipped as the control group (N=45). The anxiety of learners was determined by the Foreign Language Classroom Anxiety Scale (FLCAS) before and after the treatment in flipped and non-flipped groups comparatively. The results of this study showed a significant reduction in FLA levels in the flipped group. However, there was no significant change in the non-flipped group.