Although splenic artery aneurysm (SAA) is the commonest visceral and third most common intra abdominal aneurysm after aorta and iliac artery, aneurysm of splenic artery along with aneurysm of splenic vein with arteriovenous (a-v) fistula communication between them is a rare entity. Most are <3 cm in diameter. Giant true SAAs are rare and very few lesions >10 cm have been reported. We hereby report a case of an 18 cm x 15 cm size splenic artery and vein aneurysm with a-v fistula in an adult female nulliparous woman who presented with progressively enlarging pulsatile mass in the left upper abdomen with long-standing intractable pancytopenia and splenomegaly. Diagnosis was established by CT (computed tomogram) angiogram and laboratory tests. Laparotomy demonstrated huge well-defined aneurysm of splenic artery and vein with splenic a-v fistula, extending in all except the right lower and inferior quadrants of the abdomen along with splenomegaly. Aneurysmectomy with splenectomy was done.