This study is a descriptive research study conducted to identify factors that affect children of Korean mothers the coronavirus disease 2019 (COVID-19) preventive health behavior. It was confirmed that knowledge of COVID-19, maternal confidence, and risk perception of COVID-19 infection were related to the Preventive health behaviors of COVID-19 of Korean mothers with children. The subjects of this study were 191 mothers residing in Korea and raising children under the age of 5, and data were collected through an online questionnaire. We used the Google platform to fill out a questionnaire and collect data using a network sampling method from mothers who voluntarily participated in a survey at an online community meeting of mothers with young children. The collected data were analyzed using descriptive statistics, factor analysis, t-test, Pearson’s correlation analysis, and multiple regression analysis using IBM SPSS statistics 21.0 program. Preventive health behaviors of COVID-19 factor 1 are positively correlated with: mothers’ COVID-19 knowledge (r = 0.192, p < 0.01), confidence in infant care knowledge(r = 0.179, p < 0.05), and satisfaction with the role of mother(r = 0.351, p < 0.001). Negatively correlated with: unacceptable risk perception(r = −0.222, p< 0.01). Preventive health behaviors of COVID-19 factor 2 are positively correlated with: mothers’ COVID-19 knowledge (r = 0.166, p < 0.05), confidence in infant care knowledge(r = 0.179, p < 0.05), and satisfaction with the role of mother(r = 0.338, p < 0.001). Negatively correlated with: unacceptable risk perception(r = −0.205, p < 0.01). To strengthen COVID-19 preventive health behavior of Korean mothers with young children, it is suggested that education programs should be developed to provide accurate knowledge, increase maternal confidence, and improve the risk perception of COVID-19 infection.