INTRODUCTION: The objective of this study was to prospectively validate the “Brief Developmental Assessment”, which is a new early recognition tool for neurodevelopmental abnormalities in children with heart disease that was developed for use by cardiac teams. METHODS: This was a prospective validation study among a representative sample of 960 pre-school children with heart disease from three United Kingdom tertiary cardiac centres who were analysed grouped into five separate age bands. RESULTS: The “Brief Developmental Assessment” was successfully validated in the older four age bands, but not in the youngest representing infants under the age of 4 months, as pre-set validation thresholds were met – lower 95% confidence limit for the correlation coefficient above 0.75 – in terms of agreement of scores between two raters and with an external measure the “Mullen Scales of Early Learning”. On the basis of American Association of Pediatrics Guidelines, which state that the sensitivity and specificity of a developmental screening tool should fall between 70 and 80%, “Brief Developmental Assessment” outcome of Red meets this threshold for detection of Mullen scores >2 standard deviations below the mean. CONCLUSION: The “Brief Developmental Assessment” may be used to improve the quality of assessment of children with heart disease. This will require a training package for users and a guide to action for abnormal results. Further research is needed to determine how best to deploy the “Brief Developmental Assessment” at different time points in children with heart disease and to determine the management strategy in infants younger than 4 months old.