Although early institutionalization has been shown to have broad, detrimental effects on child developmental outcomes, there have been few attempts to systematically measure which aspects of the institution and caregiving environment associate with negative psychological outcomes. The current study uses a culturally and contextually modified early adolescent version of the Home Observation for Measurement of the Environment Inventory (EA-HOME-JP) in Japanese child welfare institutions (CWIs) to provide preliminary data on relevant variables in the caregiving environment that associate with domains of perceived self-competency. Forty-six children and young people (Agemean = 13 years 9 months) and their 35 primary caregivers from 11 CWIs were interviewed using EA-HOME-JP. Children and young people also self-reported on their perceived cognitive, physical, social competencies, and sense of self-worth. Participants within the same residential environments exhibited marked variation across each EA-HOME-JP subscale suggesting that the same rearing environment can be experienced differently by different individuals. Interestingly, EA-HOME-JP scores did not vary with care type (large-ward, middle-ward, and family-like), Instead, CWIs grouped within the same care type showed significant variation to one another on EA-HOME-JP subscales. Importantly, EA-HOME-JP scores, rather than care type, associated with aspects of competency (cognitive competency and sense of self-worth). As these findings are based on a small number of participants, they will require further replication in larger samples ascertained from other regions in Japan. Ultimately, these data may contribute to considerations over optimal packages of residential rearing in Japan.