We report a case of dissecting aneurysm of the right posterior cerebral artery presenting with sudden onset headache and altered behavior during labor. A 26-year-old P1001 with uncomplicated antenatal period, except history of headache off and on since 32 weeks of pregnancy, developed sudden onset headache and altered behavior during 3rd stage of labor. She had vaginal delivery and a live born male baby was delivered with good Apgar score. The CT was suggestive of subarachnoid hemorrhage and DSA was suggestive of dissecting aneurysm of the right P2 segment with hypoplasia of right P1 segment and A1 segment of posterior and anterior cerebral artery, respectively. The patient was managed conservatively. At 4-month follow-up, the patient was doing well. We discuss about the rare association of a dissecting aneurysm and pregnancy, especially dissection of the posterior cerebral artery.