BackgroundEarly childhood is a dynamic period of physical, psychosocial and cognitive development, where age appropriate intervention during the preschool years influences psychosocial, behavioural and academic achievement of children. This study evaluated the impact of a comprehensive preschool intervention on psychosocial, cognitive and behavioural school preparedness among children in Addis Ababa, Ethiopia.MethodsEmploying a cluster-sampling design, 150 preschool children who received the basic preschool curriculum (non-intervention) were compared with 100 randomly selected children who received a comprehensive preschool curriculum (intervention) using the Early Development Instrument (EDI) in five domains. Sample t-tests compared means of domain scores. Binary logistic regression analysed proportions of vulnerability in domains and overall.ResultThere were no group differences in gender, age, special need status or child’s first language. Intervention children had higher domain scores on social competence (mean difference 0.67 (SE=0.26)), emotional maturity (mean difference 0.77 (SE=0.29)), language and cognitive development (mean difference 0.67 (SE=0.40)), communication and general knowledge (mean difference 0.82 (SE=0.34)). Accounting for confounding variables, intervention children had a lower chance of overall vulnerability to domain problems (adjusted OR (AOR)=0.38; 95% CI 0.13 to 1.15), language and cognitive development (AOR=0.21; 95% CI 0.03 to 1.64), and social competence (AOR=0.20; 95% CI 0.08 to 0.45).ConclusionThe comprehensive intervention was associated with better outcomes on early childhood development across four domains. It is recommended to extend this programme to other areas of Ethiopia, where children do not have appropriate school preparation, to reduce risk of school dropout, negative personal and societal outcomes.