Sharing has been recognized as an asset against the societal and environmental consequences of the current crises. However, there is a lack of clear recommendations for designing user-centered shared products and services. This research addressed this gap through the development of design principles for cases involving sharing physical objects (a cooperative and distributive activity that leads a person to use a material artefact in a non-exclusive way, i.e., in common with one or more other people, for pragmatic or symbolic reasons). The recommendations are based on four studies: (1) a literature review aimed at identifying guiding principles for designing and evaluating sharing activities, (2) a cross-cultural questionnaire conducted in five countries (France, Germany, Egypt, Thailand, and Mexico) in order to test the specificity and exhaustiveness of the principles, (3) a model task aimed at assessing the reliability, efficacy, and usability of the proposed principles, and (4) an ecologically-oriented study aimed at assessing the validity of the principles against experiences with a carsharing cooperative. These studies helped iteratively refine a set of “shareability principles”. The final eight principles are: Cooperativity, Decontamination, Governance, Maintenance, Psychological Appropriation, Risk Mitigation, Support, and Value.