Introduction: Abdominal actinomycosis is a rare granulomatous inflammatory disease caused by a Gram-positive anaerobic bacterium Actinomyces israelii, manifesting as inflammatory mass, or abscess formation. Evolution is slow and steady in inflammatory contiguous extension without limit organ that lends itself to confusion with abdominal malignancies. Methods: We performed a retrospective study on the patients with abdominal actinomycosis operated in the First Surgical Clinic, "St. Spiridon" University Hospital Iasi; between 1980 - 2018 there have been 13 cases (4 men and 9 women) with a mean age 44.07 years admitted for abdominal tumors (7 cases) or pelvic inflammatory disease (6 cases). Results: We identified as predisposing factors: IUD maintained over 10 years (6 cases), foreign bodies 2 cases (a toothpick probably perforated colon, gallstones lost in peritoneum), diabetes (3 cases), immunodepression. All cases were operated by laparotomy (9 cases) or laparoscopic approach (4 cases). We describe five of these cases of actinomycosis that had been mimicking a colon cancer: ileo - cecal - 3 cases, transverse colon - one case and on the greater omentum - one case, followed by specific treatment with penicillin, with good evolution. Conclusions: Abdominal actinomycosis should always be included in the differential diagnosis of abdominal tumors. Preoperative diagnosis, difficult but possible, can avoid surgery. Treatment with antibiotics is necessary for the healing of the disease. Postoperative control is mandatory, with relapses possible.