Foreign language learning anxiety is one of the affective factors which influence language learning negatively. It has several sources and different types. The present study aimed at investigating the sources of foreign language speaking anxiety of Iranian EFL learners. To do so, 154 EFL learners participated in the study. They were required to fill out a foreign language anxiety questionnaire which was developed based on the Foreign Language Classroom Anxiety Scale (FLCAS) by Horwitz, Horwitz, and Cope (1986). The results of the study indicated that "fear of making mistakes," "fear of negative evaluation," and "lack of vocabulary knowledge" were the main factors which caused anxiety among students. Some strategies are recommended for the students to use in order to cope with the anxiety-provoking factors.