Background: Acute subdural hematoma in an infant without external signs of head trauma is sometimes thought to be symptomatic of shaken baby syndrome (SBS) in the United States or of infantile acute subdural hematoma (IASDH) due to minor head trauma in Japan. The present case report aimed to demonstrate that holohemispheric hemorrhage in dural border cell layer (HHDBCL) can be disclosed after evacuation of IASDH. Case description: A 12-month-old boy was noted by his mother falling backward and striking the occipital region. After crying, he developed convulsion followed by altered consciousness. He was brought to a nearby hospital where head CT revealed acute subdural hematoma on the right side associated with large sylvian fissure on the left side. The patient underwent emergency surgery. Via dural incision, xanthochromic fluid and flesh bloody fluid including several flesh clots were removed. His postoperative course was uncomplicated and revealed good recovery to the level same as the previous condition. Magnetic resonance imaging next day after operation disclosed thin, film-like, high-intensity hemorrhage surrounding the entire cerebral hemisphere (i.e holohemispheric hemorrhage), anatomically corresponding to dural border cell layer. Ophthalmological examination revealed bilateral retinal hemorrhages. His five years follow-up neurological examinations confirmed to have normal developmental milestones. Discussion & Conclusion: Pathoetiology causing IASDH may be secondary spread of the hemorrhage from DBCL into the subdural compartment. HHDBCL is considered to be unique neuroimaging features that may indicate primary pathoetiology causing IASDH. IASDH can occur after a short fall, if the dural border cell layer is disrupted in an infant with cranio-cerebral disproportion, including benign enlargement of subarachnoid space and or large sylvian fissure. Neuroimaging findings showing HHDBCL may be useful to make differential diagnosis between IASDH and SBS