While plenty of learning occurs outside educational environments, few studies have examined the extent and type of language learners’ out-of-class activities. This study intends to investigate the extent to which Iranian EFL learners are exposed to English reading, listening, and audiovisual materials out of the classroom and determine the relationship between this exposure and learners’ vocabulary knowledge. To this end, 88 freshman students of English language teaching major were administered a vocabulary knowledge test and a questionnaire. The reliability of both instruments was tested and approved. The results of this study indicated that the learners spent the most time on viewing English audiovisual materials, including movies, TV series, and online videos. Listening and reading were the second and last sources of out-of-class exposure to English. The results of Pearson correlation analysis revealed a positive relationship between viewing and listening to English materials and vocabulary knowledge. Moreover, it was found that using no subtitles and using English subtitles while viewing had a positive correlation with vocabulary knowledge. No significant effect was found for using Persian subtitles or reading. The findings show that the popularity of audiovisual media and their potential for vocabulary learning should be further exploited in EFL programs. It is also suggested that learners be encouraged to engage in extensive viewing.