Introduction. Adenocarcinoma of the colon is the most common histopathological type of colorectal cancer. In Western Europe and the United States, it is the third most common type and accounts for 98% of cancers of the large intestine. In Uganda, as elsewhere in Africa, the majority of patients are elderly (at least 60 years old). However, more recently, it has been observed that younger patients (less than 40 years of age) are presenting with the disease. There is also an increase in its incidence and most patients present late, possibly because of the lack of a comprehensive national screening and preventive health-care program. We describe the clinicopathological features of colorectal carcinoma in the case of a young man in Kampala, Uganda. Case presentation. A 27-year-old man from Kampala, Uganda, presented with gross abdominal distension, progressive loss of weight, and fever. He was initially screened for tuberculosis, hepatitis, and lymphoma, and human immunodeficiency virus/acquired immunodeficiency syndrome infection. After a battery of tests, a diagnosis of colorectal carcinoma was finally established with hematoxylin and eosin staining of a cell block made from the sediment of a liter of cytospun ascitic fluid, which showed atypical glands floating in abundant extracellular mucin, suggestive of adenocarcinoma. Ancillary tests with alcian blue/periodic acid Schiff and mucicarmine staining revealed that it was a mucinous adenocarcinoma. Immunohistochemistry showed strong positivity with CDX2, confirming that the origin of the tumor was the colon. Conclusions: Colorectal carcinoma has been noted to occur with increasing frequency in young adults in Africa. Most patients have mucinous adenocarcinoma, present late, and have rapid disease progression and poor outcome. Therefore, colorectal malignancy should no longer be excluded from consideration only on the basis of a patient's age. A high index of suspicion is important in the diagnosis of colorectal malignancy in young African patients.