The Change Theory of Nursing was developed by Kurt Lewin, who is considered the father of social psychology. This theory is his most influential theory. He theorized a three-stage model of change known as unfreezing-change-refreeze model that requires prior learning to be rejected and replaced.

Lewin's definition of behavior in this model is "a dynamic balance of forces working in opposing directions."

The Change Theory has three major concepts: driving forces, restraining forces, and equilibrium. Driving forces are those that push in a direction that causes change to occur. They facilitate change because they push the patient in a desired direction. They cause a shift in the equilibrium towards change. Restraining forces are those forces that counter the driving forces. They hinder change because they push the patient in the opposite direction. They cause a shift in the equilibrium that opposes change. Equilibrium is a state of being where driving forces equal restraining forces, and no change occurs. It can be raised or lowered by changes that occur between the driving and restraining forces.

There are three stages in this nursing theory: unfreezing, change, and refreezing.

Unfreezing is the process which involves finding a method of making it possible for people to let go of an old pattern that was somehow counterproductive. It is necessary to overcome the strains of individual resistance and group conformity. There are three methods that can lead to the achievement of unfreezing. The first is to increase the driving forces that direct behavior away from the existing situation or status quo. Second, decrease the restraining forces that negatively affect the movement from the existing equilibrium. Thirdly, finding a combination of the first two methods.

The change stage, which is also called "moving to a new level" or "movement," involves a process of change in thoughts, feeling, behavior, or all three, that is in some way more liberating or more productive.

The refreezing stage is establishing the change as the new habit, so that it now becomes the "standard operating procedure." Without this final stage, it can be easy for the patient to go back to old habits.