Rationale: Subdural anaplastic large-cell lymphoma (SALCL) is an extremely rare subtype of primary central nervous system (CNS) lymphoma. Here, we report a very rare subdural lymphoma case, which was misdiagnosed as a subacute epidural hematoma based on the radiological examination.Patient concerns: We present the case of an 82-year-old patient who presented with a 2-day history of headache and consciousness disorder following head injury. Computed tomography of the head revealed a fusiform isodense/slightly dense shadow under the right temporoparietal occipital cranial plate, suggesting a subacute epidural hematoma. It was initially misdiagnosed as a right traumatic subacute epidural hematoma with hemiplegia of the left limb. According to the patient's condition, an emergency craniotomy was performed to remove the hematoma. However, it was found that the lesion was located under the dura mater and was yellowish-brown with yellowish-brown liquid inside. The appearance of the lesion looked like bean curd residue. Histopathological examination diagnosed ALCL.Diagnosis: SALCL presenting as a subacute epidural hematoma on imaging.Interventions: Operation.Outcomes: The patient died 1 month after being discharged automatically.Conclusions: This report shows a rare radiography presentation of SALCL. SALCL can mimic the appearance of an epidural hematoma and should be regarded as a differential diagnosis even in patients with a history of craniocerebral injury and the "typical" imaging appearance of an epidural hematoma. The report is hoped to provide a scientific reference for the clinical diagnosis of subdural lymphoma.