Knowledge of self-continuity is proposed as essential to self understanding. However, little research has addressed the development of the extended self in very young children. This study explored ownership understanding as evidence for knowledge of the interpersonal extended self. Toddlers, age 18 months to 28 months, identified items as belonging to themselves or another, and participated in the classic mirror self- recognition task. Mothers completed the Self Development Questionnaire. Results show that the children have a basic understanding of ownership, and that this understanding differentiated children who provided self-descriptions and evaluations from children who did not. Mirror self-recognition was unrelated to ownership understanding or self-descriptions and evaluations. These results suggest that the extended self emerges earlier in development than previously claimed. Implications for integrated self-concept development are discussed.