The goal of this study was to assess attitude towards plagiarism in faculty members of Medical School at Tehran University of Medical Sciences. One hundred and twenty medical faculty members of Tehran University of Medical Sciences were enrolled in this cross-sectional study. They were asked to answer to valid and reliable Persian version of attitude towards plagiarism questionnaire. Attitude toward plagiarism, positive attitude toward self-plagiarism and plagiarism acceptance were assessed. Eighty seven filled-up questionnaires were collected. Mean total number of correct answers was 11.6±3.1. Mean number of correct answers to questions evaluating self-plagiarism was 1.7±0.4 and mean number of correct answers to questions evaluating plagiarism acceptance was 1.4±0.2. There was no significant correlation between plagiarism acceptance and self-plagiarism (r=0.17, P=0.1). It is essential to provide materials (such as workshops, leaflets and mandatory courses) to make Iranian medical faculty members familiar with medical research ethics issues such as plagiarism.