The study investigated if teaching summarizing skills could improve the summary skills of Korean EFL university students. This study involved 38 university freshmen in a required English course and were randomly chosen as the control and experimental groups. The experimental group was taught through summarizing rules, while the control group was engaged in other lessons during the intervention period. The students’ summaries were analyzed as to how effectively the participants paraphrased and integrated the main ideas, the major supporting details, and accurate information from source text into their summaries. The results show that a significant instruction effect was observed in the summary writing performance of the experimental group, in identifying main ideas and major details and paraphrasing and integrating ideas, compared to the control group, which showed a significant change between the first and second summaries only on the accuracy measure. The results are also supported by the questionnaire on students’ perceptions of the instruction.