Purpose: Purpose of this research was to identify effects of application of a modified primary nursing system. Methods: Measurement was done of direct nursing time and satisfaction of nurses and patients before and after one month of the modified primary nursing system in a surgery unit in C university hospital, Seoul. Results: There was no statistically significant difference between average for patient satisfaction (4.24) before and (4.11) after application of the modified primary nursing system. Total average for nurse satisfaction with the nursing delivery system was 2.89 before application and, 3.34 after, indicating some significant differences (t=-4.06, p<.001). The KPCS-1 was 10.19 before application of the modified primary nursing system and 9.52 after application. Recalculated into direct nursing time, the average direct nursing time for one patient was 92 minutes before application, and 85.98 minutes after, indicating no significant difference. Conclusion: Through this research an attempt was made to build and test a modified primary nursing system. Results indicate that the most important thing is to clearly regulate office work and safely implement the new system.