Objective: Hospital organizational changes are known to deteriorate nurses' organizational commitment, and the support of frontline nurse managers is crucial in preventing this deterioration. However, the effects of the practical support provided by frontline nurse managers at different subordinate career stages during organizational change are yet to be determined. Thus, in this study, we aim to clarify the associations between nurses' organizational commitment and the two types of frontline nurse manager support (i.e., preparation for organizational change and personal counseling) based on subordinate nurses' years of experience. Methods: This cross-sectional study was conducted among nurses using a self-report survey method. Hierarchical multiple regression analyses were conducted, with organizational commitment as the dependent variable. Results: Responses from 1,603 nurses at 63 hospitals were analyzed. As per our findings, both types of frontline nurse managers' practical support were found to positively and significantly affect nurses' organizational commitment. The association of these two types of frontline nurse manager support with organizational commitment based on years of nursing experience was deemed insignificant. However, the results of a subgroup analysis per career stage based on years of experience showed that organizational commitment for nurses with more than 20 years of experience was not associated with preparation for organizational change. Conclusions: Both types of practical support provided by frontline nurse managers during organizational change are important to retain nurses' organizational commitment. However, the effectiveness of each type of support may differ according to the nurses' career stage. For expert nurses, personal counseling was found to be more important than preparation.