Research in organizational change has suggested that employees’ support is needed to succeed in implementing change. This study investigated change commitment, which reflects this support and includes affective, continuance and normative change commitment. The study explored the impact of factors such as Human Resource practices and the role of the immediate supervisor on change commitment, based on the model of institutionalizing change interventions described by Armenakis, Harris, & Feild (1999). The aim was to provide empirical support for specific relations in this model and simultaneously contribute knowledge about the role of these factors. Data was gathered through interviews and questionnaires and analyzed by means of qualitative content analysis and multilevel linear regression. Participants were 34 leaders and 213 subordinates from a large Norwegian government organization. The study found that some HR practices contributed to change commitment among employees. Furthermore, the immediate supervisor organizational citizenship behavior proved important solely for affective change commitment. In addition, groups differed significantly only in this form of change commitment. Qualitative research investigated categories such as immediate supervisor attributes and their facilitating function during change. Further research should explore additional HR practices and supervisor attributes and test the model for institutionalizing change interventions in other contexts.