Student plagiarism continues to threaten academic integrity. This investigation assessed whether an inoculation message strategy could combat university plagiarism by protecting student attitudes against pro-plagiarism justification arguments. Additionally, we sought theoretical confirmation of previous findings on involvement and accessibility in inoculation, examined the effects on vested interest, and evaluated matching and mismatching strategies in terms of affect- and rationality-based inoculation treatment messages and subsequent attack messages. A total of 225 students participated in three sessions spanning six weeks. Results indicated that none of the inoculation treatments conferred resistance as measured in attitude toward plagiarism, but all treatments enhanced involvement and attitude accessibility, and the fear- and rationality-based treatments enhanced vested interest. Additionally, fear-based treatments derogated the source of the message. Results also suggest that a matching strategy is superior with both affect- and rationality-based attack messages, such that inoculation treatments are most effective when using the same argument bases (e.g., affective or rational) as the attack message. These results offer guidance for crafting communication campaign strategies to reduce the occurrence of student plagiarism offenses. (Contains 3 tables.)