The Sustained Shared Thinking and Emotional Wellbeing Scale (SSTEW; Howard et al., 2020) was developed to assess interactional quality in early childhood education and care. Although initially developed by Siraj and colleagues (2015), validation of the scale was not conducted. The first attempted validation of the SSTEW was conducted in the context of the current study. SSTEW brings together different dimensions of the Early Childhood Education and Care (ECEC) environment to consider practice that supports children aged 2–5 to develop skills in sustained shared thinking and emotional wellbeing. SSTEW contains 14 elements, which combine as five sub-scales (i.e., Social-emotional development [building trust, confidence, and independence and social and emotional wellbeing] and Cognitive development [supporting and extending language and communication, supporting learning and critical thinking, and assessing learning and language]) related to two domains of development. Data were collected from children at the end of their pre-school year. Internal consistency, concurrent validity, and predictive validity were reported. (PsycTests Database Record (c) 2021 APA, all rights reserved)