Mastery of idiomatic expressions by foreign language learners is often equated with the fluency of native speakers of that language. However, learning these idiomatic expressions is one of the significant problems experienced by learners. The present quasi-experimental study conducted over four weeks in the ELT department of a Turkish university aims to investigate the effectiveness of teaching idioms via graphic novels compared to teaching them via traditional activities. Forty most figurative idioms selected randomly from the Michigan Academic English Spoken Corpus (MICASE) were used in a script and the script was converted to a graphic novel with the use of a computer software. The results revealed that participants in the experimental group who had learned idioms through the graphic novel performed significantly better on the post-test, indicating the efficiency of the graphic novel in vocabulary teaching. The study also offers recommendations for the use of graphic novels in the teaching of vocabulary.