Colorectal cancer (CRC) remains the second leading cause of cancer-related deaths in the United States. While a decline has been observed in the older population, the occurrence of CRC in the adolescent and young adult (AYA) population has increased over the past two decades. The histopathologic characteristics and clinical behavior of CRC in AYA patients have been shown to be distinct from those of CRC in older adults. The rarer subtypes of CRC such as mucinous adenocarcinoma and signet-ring cell carcinoma are associated with a poorer prognosis compared to the more common subtypes. Here we report a case of a 20-year-old man who was diagnosed with stage IVB (T4 N2 M1, with peritoneal carcinomatosis) signet-ring cell adenocarcinoma of the colon. The scarcity of information on these rarer subtypes merits further study and investigation.