A 61-year-old male who had been regularly hemodialyzed for a year and 8 months developed a double-loculated chronic subdural hematoma (CSDH). Computed tomography (CT) revealed a heterogenous-density hematoma at the right fronto-parietal convexity. After a burr hole aspiration and irrigation, CT disclosed a residual hematoma and a septum separating the hematoma cavities. The hematoma and the septum were removed by right frontal craniotomy. At surgery, it was found that the thick septum completely separated the hematoma cavities and the outside hematoma was made up of coagula containing trabecula-like structures, and the inside hematoma consisted of old bloody fluid. Histological examination showed that the outer membrane and the septum were both thick because of the invasion by numerous lymphocytes which suggested that the intramembraneous bleeding from sinusoids split the outer membrane of an old CSDH. Double or multi-loculated CSDH should be considered in a case which is slow in recovery or aggravated after a burr hole aspiration and irrigation.