Introduction To determine the validity and reliability of the Sinhalese translation of the Edinburgh Postnatal Depression Scale (EPDS) as a screening instrument to detect antenatal and postnatal depression.Method Two hundred and sixty five antenatal women and 204 postnatal women attending the field polyclinics of the Medical Officer of Health (MOH) area Kolonnawa participated in the study. Psychiatric diagnosis based on ICD 10 Classification of Mental and Behavioural Disorders was the 'gold standard' and the receiver operating characteristic (ROC) analysis was used to evaluate the test performance of the translated EPDS for antenatal and postnatal depression separately. Reliability was tested using test-retest method and computing intra-class correlation coefficients.Results A cut-off score of 9 was selected as the best to screen for depression, in antenatal (sensitivity 90.7% and specificity 86.8%) and postnatal women (sensitivity 89.9% and specificity 78.9%). The intra-class correlation coefficients of the instrument for antenatal and postnatal women were 0.95 (95% CI = 0.82 -0.99) and 0.96 (95% CI = 0.86 -0.99). ConclusionThe Sinhalese translation of the EPDS is a valid and a reliable instrument to screen for depression in antenatal and postnatal women in Sri Lanka.