Accurate postpartum depression screening measures are needed to identify mothers with depressive symptoms both in the postpartum period and beyond. Because it had not been tested beyond the immediate postpartum period, the reliability and validity of the Postpartum Depression Screening Scale (PDSS) and its sensitivity, specificity, and predictive value for diagnoses of major depressive disorder (MDD) were assessed in a diverse community sample of 238 mothers of 4- to 15-month-old infants. Mothers (N = 238; M age = 30.2, SD = 5.3) attended a lab session and completed the PDSS, the Beck Depression Inventory-II (BDI-II), and a structured clinical interview (SCID) to diagnose MDD. The reliability, validity, specificity, sensitivity, and predictive value of the PDSS to identify maternal depression were assessed. Confirmatory factor analysis supported the construct validity of five but not seven content subscales. The PDSS total and subscale scores demonstrated acceptable to high reliability (alpha = 0.68-0.95). Discriminant function analysis showed the scale correctly provided diagnostic classification at a rate higher than chance alone. Sensitivity and specificity for major depressive disorder (MDD) diagnosis were good and comparable to those of the BDI-II. Even in mothers who were somewhat more diverse and had older infants than those in the original normative study, the PDSS appears to be a psychometrically sound screener for identifying depressed mothers in the 15 months after childbirth.