Intradiploic encephalocele is a rare condition of herniation of the brain parenchyma through the diploic space. A 52-year-old man presented with a parietal intradiploic encephalocele manifesting as an intermittent headache for 7 months. CT revealed an osteolytic lesion involving the right parietal bone. MRI demonstrated brain herniation within the diploic space. Surgery may be unnecessary in the absence of concurrent symptoms or neurological deficits. After 2 years of follow-up, symptoms were improved without neurological deficits and CT findings. We report the X-ray, CT, and MRI findings of an extremely rare case of parietal intradiploic encephalocele in adulthood.