In order to address the rising concerns about undergraduates' plagiarism in academic writing practices, a blended learning scenario (a combination of face-to-face learning with online learning) was designed and the effectiveness of it was tested. Results indicated that the students became more capable of distinguishing plagiarism cases in different scenarios, and their writing performance significantly improved by engaging in the blended learning scenario, i.e. the extent of plagiarism substantially decreased and writing quality greatly increased. Furthermore, the students mostly provided positive feedback towards the learning intervention. This study contributes to existing literature on instructional solutions to plagiarism issues by focusing on how students' understandings of plagiarism and source use can be achieved during their writing in a blended learning scenario.