Isolated splenic metastasis from colorectal cancer (CRC) is extremely rare, occurring in only 1.2–7.1% of cases, due to the spleen’s strong immune surveillance, lack of afferent lymphatic drainage, and unique blood flow. While metastasis typically spreads to the liver and lungs, haematogenous dissemination to the spleen can occur, though the exact mechanism remains unclear. Most cases are asymptomatic and discovered incidentally through imaging or rising carcinoembryonic antigen (CEA) levels. Treatment options include systemic chemotherapy, splenectomy, or a combination, depending on disease extent and patient condition. This study reports two cases of sigmoid colon adenocarcinoma initially treated with curative surgery and six months of FOLFOX chemotherapy. Both patients showed no initial metastasis but later presented with rising CEA levels (140 ng/mL). CT scans revealed isolated splenic metastases without other systemic involvement. They underwent an additional six months of chemotherapy, achieving stable disease with no complications. These cases highlight the importance of close surveillance and suggest that systemic chemotherapy alone may be a viable alternative to splenectomy in selected patients.