Recently, the patient’s role in preventing adverse events has been emphasized. Patients who are more knowledgeable about safety issues are more likely to engage in safety initiatives. Therefore, nurses need to develop techniques and tools that increase patients’ knowledge in preventing adverse events. For this reason, an educational smartphone application for patient safety called “Safe Patients” was developed through an iterative process involving a literature review, expert consultations, and pilot testing of the application. To determine the effect of “Safe Patients,” it was implemented for patients in surgical units in a tertiary hospital in South Korea. The change in patients’ knowledge about patient safety was measured using seven true/false questions developed in this study. A one-group pretest and posttest design was used, and a total of 123 of 190 possible participants were tested. The percentage of correct answers significantly increased from 64.5% to 75.8% (P < .001) after implementation of the “Safe Patients” application. This study demonstrated that the application “Safe Patients” could effectively improve patients’ knowledge of safety issues. This will ultimately empower patients to engage in safe practices and prevent adverse events related to surgery.