We report a rare case of pneumorrhachis following lumbar puncture. A 4-year-old boy was admitted to our hospital with seizures following a head injury and upper respiratory infection. Lumbar puncture was performed to rule out central nervous system infection. In response to leg pain and weakness a few hours after the procedure, lumbar spine computed tomography (CT) revealed pneumorrhachis at the level of L5-S1. In a follow-up CT scan 3 days later, the pneumorrhachis resolved spontaneously. Pneumorrhachis following diagnostic lumbar puncture is an extremely rare condition. We discuss pneumorrhachis and review cases in the literature.