The association between inflammation, platelets, and patent ductus arteriosus (PDA) has not been studied so far. The purpose of this study was to evaluate whether C-reactive protein (CRP) is related to low platelet count and PDA. This was a retrospective study of 88 infants with a birth weight ≤1500 g and a gestational age ≤30 weeks. Platelet count, CRP, and an echocardiogram were assessed in all infants. The subjects were matched by sex, gestational age, and birth weight. Differences were compared using the χ2, t-test, or Mann–Whitney U-test, as appropriate. Significant variables were entered into a logistic regression model. The association between CRP and platelets was evaluated by correlation and regression analysis. Platelet count (167 000 vs. 213 000 µl−1, p = 0.015) was lower and the CRP (0.45 vs. 0.20 mg/dl, p = 0.002) was higher, and the platelet count correlated inversely with CRP (r = −0.145, p = 0.049) in the infants with vs. without PDA. Only CRP was independently associated with PDA in a logistic regression model (OR 64.1, 95% confidence interval 1.4–2941, p = 0.033). Fil: Meinarde, Leonardo. Instituto Universitario de Ciencias Biomédicas de Córdoba; Argentina Fil: Hillman, Macarena. Instituto Universitario de Ciencias Biomédicas de Córdoba; Argentina Fil: Rizzotti, Alina. Instituto Universitario de Ciencias Biomédicas de Córdoba; Argentina Fil: Basquiera, Ana Lisa. Instituto Universitario de Ciencias Biomédicas de Córdoba; Argentina Fil: Tabares, Aldo. Hospital Privado Centro Medico de Córdoba; Argentina Fil: Cuestas, Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Ciencias de la Salud. Universidad Nacional de Córdoba. Instituto de Investigaciones en Ciencias de la Salud; Argentina