Excess body weight is associated with increased risk of colorectal cancer. Obesity surgery (OS) is increasingly performed in individuals who are morbidly obese. Increased CRC risk was particularly evident greater than ten years after OS and was similar for gastric bypass, gastric banding and gastroplasty. By contrast, CRC risk in non-operated obese individuals remained stable according to the literature review. We present a 35 year old male, who underwent laparoscopic gastric bypass and cholecystectomy in 2009. Then in 2018, the patient had revision laparoscopic bypass. He lost 33 kg with bariatric surgery. After six months from revision surgery with bilateral leg swelling which was associated with episodes of loss of consciousness. He was admitted to the hospital and initial blood tests revealed hypoalbuminemia (1.85 g/dl) and anemia (Hemoglobin level 8.1). The patient managed conservatively with albumin and protein supplements. Reviewed by the dietician and started on diet plan for his malabsorption. The patient generally improved for few weeks then deteriorated with watery diarrhea. Investigations showed pancreatic elastases deficiency and low zinc level. He was started on pancreatic enzymes replacement, and multivitamins. Diarrhea was ongoing without improvement, hence additional investigations were done. Labs revealed elevated transaminases. Fibro-scan showed normal liver. Tumor markers were highly elevated CA 199 levels. Colonoscopy was performed. There was a lesion in the rectum showed rectal adenocarcinoma. The patient was referred to oncology team for further management. Our case highlights the potential risk of delayed diagnosis of colorectal cancer (CRC) after OS. Diarrhea after OS, mainly those with malabsorptive elements, is common. Multiple factors exert their influence on bowel habits; preoperative comorbidities and procedure-related aspects are intertwined with postoperative nutritional habits. Diarrhea may unmask underlying CRC. The risk of CRC increasing with time from OS, which would be consistent with the long natural history of colorectal carcinogenesis. It is plausible that colorectal carcinogenesis may be driven by changes in diet and the gut microbiota post-bariatric surgery. Another explanation that can be added, possible carcinogenetic action of the unabsorbed food and bile acid on colonic mucosa. Thus, diagnosis of CRC post OS can be challenging. Our case reflects CRC as a potential cause of chronic diarrhea post OS and the importance of keeping it in the differentials diagnoses while evaluating diarrhea in this specific patient population.