Plagiarism in ESL and EFL learning contexts has become a topic engaging many researchers in a hot debate in recent years. Comparisons of student-generated texts with their source texts have shown that students rely amply on source texts in their writings, using copying as a major strategy. The students themselves relate these problems to their confusion of how to cite. Nevertheless, little research has been conducted on what constitutes effective citation practices in student writing. The present study aims at measuring the effects of teaching anti-plagiarism strategy of proper citation on 19 postgraduate and 34 graduate students' use of multiple sources in their writings. The instructional treatment conducted in 30 min per week for seven sessions, aimed at teaching correct quotation rules and different functions of citation (i.e., presenting the literature in the field, comparing the existing views, supporting the writer's view, etc.), while emphasizing the recognition of these rules at work. The writing samples of the students were three citation tests and source-based writing tasks assigned before, during, and after the treatment. Then the effective citation strategies of the students were analyzed according to their use of standard citation in APA (American Psychological Association) style. The results of the assigned tasks and one survey question demonstrated students' perceived growing confidence and significant improvements in their citation skills in their source-based writings. The results can yield insightful implications for writing course designers to treat significant problems of the students in their academic writings.