Plagiarism has recently turned into a major concern for academics and academic institutions. Nevertheless, the reasons behind it continue to be obscure. Available statistical findings do not provide a very clear picture of the scale and nature of plagiarism; neither do they clarify the extent to which this phenomenon is changing through time or is different from country to country, from subject to subject, or among undergraduate and graduate students. Accordingly, the present study was carried out to investigate EFL University professors' and students' perceptions of the nature and causes of plagiarism. The participants consisted of 20 EFL university professors and 40 university students studying TEFL at MA and PhD levels. Their responses to a 30-item Likert-Scale questionnaire demonstrated that both groups were equally aware of the nature of plagiarism and the related ethical issues, while the students had considerably different standpoints regarding the excuses and punishments for plagiarism.