Abstract Background Although it is known that portomesenteric venous thrombosis (PMVT) is associated with total colectomy and proctocolectomy in young patients with inflammatory bowel disease, little is known about incidence and risk factors of PMVT among the elderly population undergoing colorectal surgery for cancer. Methods Data of elderly patients (> 70 years) undergoing surgery for colorectal cancer were retrospectively registered. The occurrence of PMVT was correlated with the patients’ characteristics and operative variables. Data collected included age, sex, obesity, ASA score, tumor degree, type of surgical resection, surgical approach (laparoscopic or open), and duration of surgery (from skin incision to the application of dressings). Results A total of 137 patients > 70 years who underwent surgery for colorectal cancer and developed an acute intraabdominal process with suggestive symptoms, needing a CT scan, were included. Three of these patients (2.1%) had portomesenteric venous thrombosis during the study period, which was proved with CT scan. There were no significant patients’ characteristics or operative variables between patients with or without the occurrence of PMVT after surgery. Of interest, only operative time was significantly higher in patients with PMVT after surgery (256 ± 40 vs 140 ± 41, p < 0.001). Conclusions PMVT as a cause of abdominal pain after colorectal surgery for cancer in the elderly population is uncommon. An index of suspicion for PMVT in an elderly postoperative colorectal cancer patient with sudden onset of abdominal pain must be maintained.