Pentraxin 3 (PTX3) is an acute phase protein. Our goal was to assess PTX3 as a predictor of systemic inflammatory response syndrome (SIRS), death and disease severity in acute pancreatitis (AP) in comparison to C-reactive protein (CRP) and the APACHE II score. From April 2011 to January 2015, 142 patients with AP were included in this single center post hoc analysis of prospectively collected data at the University Hospital Basel, Switzerland. Disease severity was rated by the revised Atlanta criteria (rAC). Inflammatory response was measured by the SIRS criteria. PTX3, CRP and APACHE II score were measured. Patients median PTX3 plasma concentrations in AP were higher in moderate (3.311 ng/ml) and severe (3.091 ng/ml) than in mild disease (2.461 ng/ml). Overall, 59 occurrences of SIRS or death were observed. In the prediction of SIRS or death, PTX3 was inferior to CRP and APACHE II, with modest predictive discriminatory ability of all three markers and AUC of 0.54, 0.69 and 0.69, respectively. Upon combination of CRP with PTX3, AUC was 0.7. PTX3 seems to be inferior to CRP and APACHE II in the prediction of SIRS or death in AP and does not seem to improve the predictive value of CRP upon combination of both parameters.