Pelvic meningocele is an uncommon condition and is frequently asymptomatic. The diagnosis easily can be mistaken as ovarian cyst on pelvic sonography. In many reported cases, the diagnosis was made during laparotomy for presumed ovarian cysts. Myelography, computerized tomography (CT), or magnetic resonance imaging (MRI) is useful for definitive diagnosis. A 49-year-old woman, who had a normal diagnostic laparoscopy 3 years prior, was referred for a persistent ovarian cyst. Repeat laparoscopy revealed a retroperitoneal cyst in the left pelvic sidewall. Both ovaries and fallopian tubes were normal. Subsequent CT and MRI were used to diagnose pelvic meningocele. We speculate that pelvic meningoceles can be missed during laparoscopy due to the increased intraperitoneal pressure and the potential reduction in the cerebrospinal fluid pressure at the lumbosacral level.