Aim: The ability of neutrophil CD16 (nCD16) expression to predict outcome in complicated intraabdominal infections (cIAIs) has not yet been studied; therefore we aimed to evaluate its potential prognostic value in such patients. Methods: Between November 2018 and August 2021 a single-center prospective study was performed in the Department of Surgical Diseases at a University Hospital Stara Zagora. A flow cytometry was used to measure the levels of nCD16 before surgery and on the 3rd postoperative day (POD) in 62 patients with cIAIs. Results: We observed a mortality rate of 14.5% during hospitalization. Survivors had significantly higher perioperative expression of nCD16 than nonsurvivors (P 5 0.02 preoperatively and P 5 0.006 postoperatively). As predictor of favorable outcome we found a good predictive performance of preoperative nCD16 (AUROC 5 0.745) and a very good predictive performance of postoperative levels (AUROC 5 0.846). An optimal preoperative threshold nCD16 5 34.75 MFI permitted prediction of survival with sensitivity and specificity of 66.7% and 77.8%, respectively. A better sensitivity of 72.5% and specificity of 85.7% were observed for threshold 5 54.8 MFI on the 3rd POD. Conclusion: Perioperative neutrophil CD16 expression shows a great potential as a predictor of favorable outcome in patients with cIAIs.  Kulcsszavak: nCD16, cIAIs, intra-abdominal infections mortality, prognostic, biomarkers