Background The INTER-NDA is a novel assessment of early child development measuring cognition, language, motor skills, behaviour, attention, and socio-emotional reactivity in 2 year olds in 15 minutes. Here, we present the results of an evaluation of the INTER-NDA against the Bayley Scales of Infant Development III edition (BSID-III), its sensitivity and specificity and its psychometric properties. Methods Eighty-one infants from Oxford, UK, aged 23.1–28.3 months, were evaluated using the INTER-NDA and the BSID-III. The agreement between the INTER-NDA and the BSID-III was assessed using interclass correlations (for absolute agreement), Bland-Altman analyses (for bias and limits of agreement), and sensitivity and specificity analyses (for accuracy). The internal consistency of the INTER-NDA and uni-dimensionality of its subscales were also determined. Results The interclass correlation coefficients between the BSID-III and the INTER-NDA cognitive, motor and behaviour scores ranged between 0.745 and 0.883 (p<0.001). The Bland-Altman analysis showed little to no bias in the aforementioned subscales. The sensitivity and specificity of INTER-NDA cognitive scores 1 SD below the mean are 66.7% and 98.6% respectively, with moderate agreement between INTER-NDA and BSID-III classifications (κ = 0.72, p<0.001). The sensitivity and specificity of INTER-NDA scores <2 SD below the mean, in predicting low BSID-III scores (<70), are 100% each for cognition, and 25% and 100% respectively for language. More than 97% of children who scored in the normal range of the INTER-NDA (<1SD below mean) also scored in the normal range in the BSID-III (85). The INTER-NDA demonstrates satisfactory internal consistency and its subscales demonstrate good unidimensionality. Conclusion The INTER-NDA shows good agreement with the BSID-III, and demonstrates satisfactory psychometric properties, for the assessment of ECD at 22–28 months.