We report a case of abdominal actinomycosis, a chronic suppurative infection caused by bacteria of the genus Actinomyces, simulating colon cancer, and presenting with abdominal pain and leukocytosis. Computed tomography revealed a mass lesion with irregular contours, infiltrative aspect, with extension to omental fat and abdominal wall, in the transverse colon. A surgical intervention was performed due to the suspicious of a colonic tumor. In the post-operative period, anatomopathological examination showed suppurative nodules associated with actinomycetes colonies, confirming the diagnosis of abdominal actinomycosis. After surgery, the patient was submitted to antibiotic treatment and no relapse was observed.