The mental state in which an individual claims an object as theirs is called psychological ownership. Psychological ownership is associated with motives, routes, affordances, and outcomes directly linked to attachment. This research introduces psychological ownership in the context of designing object attachment and identifies affordance principles that help facilitate it. A framework presenting the motives for and routes to psychological ownership is proposed to provide a holistic understanding of object attachment. In the framework each route to psychological ownership, that is, control, intimate knowledge, and self-investment, has a corresponding class of affordances. Overall a total of 16 affordance principles are identified through contextual inquiry with 4 objects (a car, a mobile phone, a pair of shoes, and a park bench). Previous studies have identified various elements of this framework but have fallen short of clearly defining and relating the motives, routes, and affordances to psychological ownership identified here. These affordance principles are readily mapped to experience design models and provide a practical resource for designers. Together, the framework and the affordances inform design decisions and move towards a prescriptive design method for facilitating object attachment.