Some evidence has emerged in recent years that plagiarism can be reduced through the use of online mastery tests that are designed to train introductory psychology students in awareness of academic integrity and referencing conventions. Although these studies demonstrated a reduction in incidents of plagiarism they did not directly examine whether the use of mastery tests influenced students' attitudes toward or understanding of plagiarism. Consequently, the authors examined students' awareness of plagiarism and their perception of the seriousness of plagiarism before and after completing an online academic-integrity mastery module in a psychology course. Both students' awareness of plagiarism and their perception of the seriousness of plagiarism increased significantly from before to after completing the online academic-integrity training. Additionally, first-year students who completed the mastery modules showed better awareness of plagiarism and perceived plagiarism to be more serious as compared with a group of second-year students who had not completed the mastery modules in their first year. These results suggest that the use of academic-integrity mastery tests may improve students' awareness of, and attitudes toward, plagiarism.