Sclerosing mesenteritis (SM) is a rare, benign inflammatory disorder of unknown etiology, affecting the membranes of the digestive tract that involves lymphoplasmacytic inflammation, fat necrosis, and fibrosis of the mesentery. We report a child patient with a history of recurrent abdominal pain and fever who was found to have an intra-abdominal mass suspicious for malignancy. A tissue biopsy revealed the diagnosis of SM associated with IgG4-related systemic disease. The patient is currently maintained on 5 mg prednisone daily and no recurrence of symptoms was noted during the 24-month follow-up period. We emphasize, therefore, that SM can present clinical challenges and the presence of SM should cue clinicians to search for other coexisting autoimmune disorders that can have various outcomes.