Purpose: The purpose of this study was done to investigate the effects of oral care using 0.12% chlorhexidine and saline solution on oral status, incidence of oral pathogens and pneumonia among children who had cardiac surgery. Methods: The study participants were 84 children who underwent cardiac surgery and were admitted to the SICU of a university hospital. Oral care was provided with 0.12% chlorhexidine to the experimental group (n=43) and with saline solution to the control group (n=41), 3 times a day for 3 days. Before and after the intervention, the oral status, oral swab culture, and CPIS were checked. Results: There was no significant difference in oral status score between the two groups. The incidence of oral pathogens in the experimental group was significantly lower than that of the control group (t=-5.780, p<.001). The CPIS in experimental group was significantly lower than that of control group (t=-3.665, p<.001). Conclusion: The oral care with 0.12% Chlorhexidine is more effective than with only saline solution for reducing incidence of oral pathogens and pneumonia.