The Journal of Teaching Language Skills (JTLS) 7 (3), Fall 2015, ISSN: 2008-8191 pp. 1-28               Akbar Abbasi Bagherianpoor ∗ Assistant Professor Vali-Asr University akabbasi@gmail.com Fateme Hosseini MA, TEFL Vali-Asr University fhosseinif@yahoo.com Gholam Reza Rohani Assistant Professor Vali-Asr University rrohani@gmail.com Abstract The current study aims at exploring the role of causativization as one of the causes stated in the literature for overpassivization of English unaccusatives in an Iranian context. The study was conducted using three data collection procedures, an Oxford Placement Test, a Grammaticality Judgment Task, and a Production Task. The results revealed that causativization errors with non-alternating unaccusatives were common errors among Iranian English Majors. Level of language proficiency was a significant factor in the learners’ performance at both comprehension and production levels. There was a statistical significant correlation between the participants’ performances in the causativization and passivization errors with non-alternating verbs. The obtained results made it clear that language learners encounter serious problems in the acquisition of the verbs, and that more exposure to language input, explicit teaching of the verbs structures, and practice in different contexts can improve the situation. Keywords: alternating unaccusatives, causativization, non-alternating unaccusatives, overpassivization Received: 07/11/2015 Accepted: 09/02/2016 ∗ Corresponding author