This study explored the relation between childcare quality (staff-child ratio and staff-child interactions) and behavioural development between the beginning and the end of the childcare year among a sample of 44 low-income Latino four-year-olds in 14 childcare programmes. Neither staff-child ratio nor staff-child interactions were related to children's behaviour at the beginning of the childcare year. Further, staff-child ratio was not significantly related to changes between the beginning and the end of the childcare year in children's behaviour skills. However, staff-child interactions characterised as warm and involving direct instruction related to the development of positive social skills (e.g. taking turns, solving peer conflicts) were significantly associated with decreases in children's behaviour concerns from the beginning to the end of the childcare year. Staff-child interactions characterised negatively (e.g. overly controlling, strict scheduling) were also associated with decreases in children's behaviour concerns. Implications for improving behaviour skills of low-income Latino children by adjusting non-familial childcare features and measurement of childcare features are discussed.