The article deals with a “sense of ownership” concept. Conditions for its actualization or deactivation are substantiated. Sense of ownership is defined as a subjective emotional experience of a person regarding the belonging to him/her of certain targets of ownership. It reflects the meaning and content which real or abstract, concrete or generalized targets of ownership have, that is all can be called as “my” or “our”. Individual psychological space is a platform where a sense of ownership can be manifested. And it includes a complex of physical, social and purely psychological phenomena with which a person identifies ownself. The experience of ownership feeling can both contribute to the formation of responsibility and development of value-semantic sphere and have negative consequences, such as a feeling of personal loss, interpersonal conflict, reluctance to accept advice and resistance to change. Sense of ownership as a social-psychological phenomenon in the structure of personality can perform signaling, coordinating, motivational, evaluative and expressive functions. Three ways of actualizing the formation and realization of a sense of ownership are identified: control, intimate knowledge, and self-investing of their forces, knowledge, efforts due to the target of ownership. The realization of a sense of ownership depends on the content of both economic and non-economic social practices, the social value of the property, socio-cultural traditions of cooperation and competition in interaction, features of interpersonal interaction with appropriation. The most suitable for operationalization and diagnostics indicators of the sense of ownership manifestation are formulated. They can be used for empirical research among various categories of population and, generally, society: sense of ownership manifestation in various areas of individual psychological space (body, territory, money, personal things, scheduling, social relations, values, ideas, personal virtual space), modality, intensity, duration, depth, level of awareness, complexity, different conditions of origin, functions performed depending on the situation, forms of manifestation.