Background: Mesenteric cysts are very rare abdominal growths, generally asymptomatic, and which are usually detected incidentally white performing a physical examination or an imaging test. Complications such as infections, haemorrhage, torsion, rupture, or bowel obstruction, are seldom found in this pathology, but they can be a cause of acute abdomen. The purpose of this report is to describe the characteristics and the clinical outcome of a male patient with an infected mesenteric pseudocyst of the jejunum. Clinical case: A 49 year-old male was admitted to the emergency department with 6-day onset of abdominal pain, bowel obstruction signs, palpable tumour located in the upper hemiabdomen, systemic inflammatory response syndrome, 36,100/mm(3) white cells, 4.21 ng/ml procalcitonin, abdominal computed tomography scan with evidence of a mesenteric cystic tumour. An exploratory laparotomy was performed, finding the presence of a mesenteric pseudocyst of the jejunum with infection signs, extirpated and sent for histopathological examination. The clinical progress of the patient was satisfactory with the discharge of the patient 7 days after the surgical intervention. Conclusion: These cysts can debut as an acute abdomen due to haemorrhage, infection, obstruction and/or bowel perforation, complications can be life threatening if not detected and surgically treated at an early stage by performing a resection of the pseudocysts, with or without bowel resection, depending on the location and the size of the cyst. (C) 2015 Academia Mexicana de Cirugia A.C. Published by Masson Doyma Mexico S.A.