Klippel-Trenaunay syndrome (KTS) is a rare congenital vascular disorder involving varicosities, cutaneous vascular malformations, and hypertrophy of soft tissues and bones. It is often linked to PIK3CA gene mutations. It affects the lymphatic, capillary, and venous systems. The diagnosis is usually based on clinical presentation, supplemented by magnetic resonance imaging (MRI) and computed tomography (CT) imaging. This case involves a 43-year-old male diagnosed with KTS after presenting with severe anemia (hemoglobin 2.5 g/dL) and left lower limb swelling with varicosities. Investigations revealed hepatosplenomegaly, hemangiomas, rectosigmoid malformations, an enlarged inferior vena cava (IVC), and vascular congestion. MRI confirmed an extensive veno-lymphatic malformation in the left lower limb. The case highlights KTS's complex presentation, emphasizing the importance of timely diagnosis, multidisciplinary care, and ongoing monitoring to manage its complications. Further research is needed to enhance treatment strategies for this rare condition.