The researcher studied the process of transformation among 16 married and cohabiting couples. Research focused upon co-created transformation, a profound change in lifestyle and relationship stemming from a collaborative effort to (1) address incongruities between a couples' lifestyle and mutually held values, and (2) enhance their mutual fulfillment and quality of life.;After focusing the research upon four exemplary couples, a four-stage model of co-created transformation emerged. The four stages include (1) acknowledging incongruity, (2) generating preferences, (3) widening the circle, and (4) continuing the journey. The model is founded upon three necessary conditions, which include (1) basic needs, (2) relational resources, and (3) intellectual resources. Alternate case analysis is included. Co-created transformation is compared with another stage model, the transtheoretical model of change. Comparison serves in part to validate the model of co-created transformation and raises questions for further research.;The model of co-created transformation is a substantive level theory that merits further investigation. It is anticipated that the model may assist couples contemplating transformation, human service professionals guiding a transformation, and scholars investigating change. Given the aging and upcoming retirement of baby-boomers, this model is timely as members of this demographic group begin to consider their next steps in life.