This research examines whether relationships between change resistance and its consequences and antecedents strengthen or weaken over time during an extended duration of organizational change. In 40 health care clinics undergoing a 3-year period of significant organizational changes, we found that resistance to change had increasingly negative relationships over time with two important consequences: employees’ commitment to the organization and perceptions of organizational effectiveness. That these relationships became stronger (rather than weaker) over time suggests festering effects of resistance to change. We also found that over time supportive leadership was increasingly impactful in reducing change resistance. A major implication of this research for practice is that it is important for change agents to address employee resistance because, left unchecked, it can fester and increasingly inflict harm. Also, engaging in supportive leader behaviors can be particularly useful in ameliorating resistance to change at later stages of a change initiative.