This study is a quasi-experimental study with a non-equivalent control group pretest-posttest design conducted to determine the effect on knowledge and performance confidence in injection safety by applying an injection safety education program using a mobile application to nursing students. The study subjects were 49 second-year nursing students at a university in C province. Data analysis was performed by using the IBM SPSS 26.0 program. The experimental group was provided with printed materials on injection safety and the mobile application, while the control group was provided with the printed materials only. Both groups were allowed to self-study for seven days. General characteristics were analyzed with descriptive statistics. The homogeneity between the two groups was analyzed using a t-test, χ2 test, Mann-Whitney U test, and Fisher’s exact test, and pre-and post-test differences in knowledge and performance confidence between the experimental and control groups were analyzed with an independent t-test. The experimental group had significantly higher knowledge of injection safety (t=3.07, p=.004) and performance confidence (t=3.53, p=.001) than the control group. In addition, the difference in scores of knowledge (t=2.20, p=.034) and performance confidence (t=3.08, p=.003) in the experimental group significantly improved, compared to the control group. This study identified that the injection safety application was effectively improved nursing students’ injection safety knowledge and performance confidence. In addition, the results of this study will provide substantial evidence for the use of applications as an educational medium for nursing students’ injection safety practices in the future.