Gastrointestinal stromal tumors are the most common mesenchymal tumors of the gastrointestinal tract. They are generally considered as solitary tumors. Here we report the case of a 66-year-old man with familial history of digestive cancers, admitted after a 2-months history of gastrointestinal bleeding. Colonoscopy showed a circumferential ulcerated tumor of the sigmoid which was a well differentiated adenocarcinoma on biopsy. Computerized tomography showed only the lesion of the sigmoid. The patient underwent a left colectomy followed by immediate end-to-end anastomosis. Per-operatively, jejunal mass was discovered and a jejunal segmentectomy was performed. Pathologic examination revealed a colic adenocarcinoma pT2N0M0 associated with a low risk stromal tumor of the jejunum CD117+ and DOG-1+. No adjuvant therapy was given. After 64 months of follow-up, the patient showed no evidence of recurrence. Clinicians should be aware of the coexistence of malignancies and carry careful investigations for accurate diagnosis and better patients' prognosis.