Objectives: This study aimed to identify the factors influencing the intention of COVID-19 infection preventive behaviors among patients undergoing hemodialysis by applying the theory of planned behavior. Methods: The study included 209 patients with chronic renal failure undergoing hemodialysis at five hospitals in Gangwon-do, Korea. Data were collected from December 28, 2021 to January 15, 2022. The analysis involved percentage, mean and standard deviation, independent t-test, ANOVA, Pearson’s correlation coefficient, and hierarchical multiple regression using SPSS 22.0. Results: Significant correlations were observed between attitude toward COVID-19 preventive behavior, subjective norms regarding COVID-19 preventive behavior, perceived behavior control of COVID-19 preventive behavior, restricted dietary control, COVID-19 knowledge, self-efficacy in COVID-19 preventive behavior, and intention of COVID-19 infection preventive behavior. Hierarchical multiple regression analysis revealed that subjective norms regarding COVID-19 preventive behavior (β = 0.49, p < 0.001) and perceived behavior control of COVID-19 preventive behavior (β = 0.26, p < 0.001) significantly influenced the intention of COVID-19 infection preventive behavior among hemodialysis patients. The model accounted for 54.8% of the variance (F = 43.02, p < 0.001). Conclusions: Identifying relevant factors associated with COVID-19 preventive behaviors among vulnerable hemodialysis patients is crucial for providing adequate care by healthcare professionals. Proactive measures are necessary to prevent and manage the infection in this patient population.