This study aims to investigate the errors of prepositional verbs in Korean university students' essays and alert teachers to the necessity of a more systematic instruction of prepositional verbs. Prepositional-verb errors found in the learner corpus of essays written by 416 Korean university students were classified into five categories: (a) preposition omission, (b) wrong prepositions, (c) preposition addition, (d) misordering, and (e) others. Of the 1317 tokens of prepositional verbs retrieved from the corpus, 448 were found to be used erroneously, over half of which were instances of preposition omission. No tokens of misordering errors were found (e.g., *to go school / *go school to). A careful analysis of these errors also revealed the following. First, students were not able to discern the difference between a verb used transitively and the same verb used as a prepositional verb (e.g., believe and believe in). Second, the inability to distinguish transitive verbs from intransitive ones also resulted in a considerable number of errors in preposition omission (e.g., *listen music) and preposition addition (e.g., *enter in university). Third, using wrong prepositions (e.g., *worried at me) was also a rather common occurrence, accounting for 18% of the all the errors related to prepositional verbs.