This study aimed to explore the impact of computer-assisted language learning on Iranian EFL students’ vocabulary learning. Participants of the study were 76 students – 29 males and 47 females – learning English as a foreign language in Parto, Sadr, Poyesh and Andishe Institutes in Ahvaz who were selected after taking the Nelson English Language Test as a proficiency test. They were randomly divided into two groups. One group was taken as control and the other as experimental group. Both groups participated in the teacher-made test of vocabulary, Vocabulary Levels Test (VLT), and Word-Associates Test (WAT) as pre-test. During class sessions the control group was taught the vocabulary, in the conventional way, through the printed textbook while the experimental group taught by the software version of the same book. Three ANCOVAs were run to compare the performance of experimental and control groups after the treatment period. The results of the ANCOVAs revealed that using vocabulary learning software was more effective than using printed book on vocabulary learning, vocabulary breadth, and vocabulary depth of the participants. The results of the present study could help EFL course book designers, foreign language institutes, educational planners, material developers, teachers, and learners to provide a better context for EFL learning. Keywords: computer-assisted instruction, computer-assisted language learning, information communication technology, vocabulary breadth, vocabulary teaching software