Retroperitoneal cystic lymphangiomas are very rare lesions and may be misdiagnosed. Longstanding lymphangiomas may show secondary changes like inflammation, hemorrhage, fibrosis and rarely ossification. Treatment is complete surgical excision. We are reporting a rare case of ossifying retroperitoneal lymphangioma in a pregnant woman which was misdiagnosed clinically as ovarian tumor. Our diagnosis was confirmed by IHCCD- 31 and D2-40 positivity. Postoperative follow up for 3 years, patient is fine and she is full term pregnant now.