The Edinburgh Postnatal Depression Scale (EPDS) is the instrument most used worldwide for screening of Post-Partum Depression (PPD). The SRQ20 questionnaire has been largely used for screening of minor psychiatric disorders. This study aimed to compare the accuracy of the two instruments in screening for PPD. At the third-month follow-up home visit to infants of the 2004 Pelotas Birth Cohort, Southern Brazil, a sub-sample of 378 mothers was selected. Among other questions, EPDS and SRQ20 were applied by trained fieldworkers. Up to 15 days later, a mental health professional re-interviewed the mother (the gold standard interview). Sensitivity and specificity of each cutoff point were calculated for EPDS and SRQ20 and the results were plotted at a ROC curve. The areas under both curves were compared. Highest sensitivity and specificity cutoff were observed for EPDS ≥ 10 (sensitivity 82.7%, 95%CI 74.0 – 89.4; specificity 65.3%, 95%CI 59.4 – 71.0) and for SRQ20 ≥ 6 (sensitivity 70.5%, 95%CI 60.8 – 79.0%; specificity 75.5%, 95%CI 70.0 – 80.5%). Shape of ROC curves and areas under both curves were virtually identical (respectively, 0.8401 ± 0.02 for EPDS and 0.8402 ± 0.02 for SRQ20; p = 0.9). In conclusion SRQ20 showed to be as valid as EPDS as a screening tool for PPD at third month after delivery.