Background: Because plagiarism is such a common form of academic dishonesty, many instructors are seeking ways to effectively teach students to avoid plagiarism. Objective: The current study tested the effectiveness of a 3-pronged intervention to teach students in an upper-level psychology course to better understand plagiarism. Method: The intervention involved three different assignments across the first part of the semester: an online plagiarism tutorial, an in-class lecture over a plagiarism handout, and a follow-up homework exercise that helped students apply what they learned from the tutorial and handout. Results: Study 1 showed that students in the intervention class scored higher on an end-of-semester plagiarism test compared to a control group of classes that did not use the intervention. Study 2 replicated these results and ruled out the possibility of preexisting differences in plagiarism knowledge by comparing plagiarism test scores on a beginning-of-semester pretest and an end-of-semester posttest in both the intervention and control classes. Conclusion: The results of this naturalistic, quasi-experimental study suggest that multiple exposures to anti-plagiarism instruction in different formats can be effective. Teaching Implications: Psychology instructors can improve students' understanding of plagiarism and how to avoid it by using this 3-pronged approach in their courses.