This paper reports a case of the huge ovarian cyst in a single woman aged 16 years who has been misdiagnosed as tuberculous Peritonititis and treated accordingly. On abdominal circumference is measured at 85cm and the upper margin of cyst is extended up to xyphoid process, Upon entering the abdominal cavity. A huge peduncularted ovariman cyst origination from fight ovary is observed. Cyst is multiloculated and the cystic wall represents bluish tinged gray colored appearance. The total weight of cyst removed measures at 14,030grams. The pathological feature is reported pseudomucinous cystadenoma.