With the increased use of digital materials, undergraduate writers in English as a foreign language (EFL) contexts have become more susceptible to plagiarism. In this study, the researchers designed a blended English writing course with an online writing tutorial system entitled "DWright." The study examined the effectiveness of the online writing tool for helping a group of EFL sophomores in Taiwan develop plagiarism avoidance knowledge, paraphrasing skills, and citation abilities. Mixed-method data included pretest, posttest, and delayed test, a feedback sheet, writing assignments, interviews, and a post-course questionnaire, which reported increased awareness on plagiarism avoidance with evidence such as qualitative paraphrasing improvement and positive feedback on the use of DWright for developing plagiarism avoidance knowledge and citation competence. Pedagogical implications for researchers and instructors interested in blending online writing tutorials into their courses for plagiarism avoidance were also discussed.