This investigation focuses on the ontogeny of the inner working model (IWM) of attachment during preschool age, specifically on preschoolers' knowledge about children's and caregivers' behavioral options in attachment-related situations. The study included two cross-sectional samples of children between 3 and 6 (N = 86) and 3 and 7 years (N = 95), respectively. Children's knowledge was assessed using a picture book with attachment-related stories. Findings show an increase of attachment-related knowledge with the most rapid changes from 4 to 5 years. Moreover, children had more profound knowledge about their own behavior than about their mother's behavior and only restricted knowledge about behavior of other parent-child dyads. Regarding the quality of behavioral strategies analyses indicated the prominent role of child seeking help and autonomous coping and parental instrumental and emotional support. Consistent with cognitive theories about the development of domain-specific knowledge, the results indicate that the IWM may be conceptualized as a "theory of attachment."