BACKGROUND Primary central nervous system diffuse large B-cell lymphoma (DLBCL) is an extremely aggressive brain disease that rarely affects immunocompetent non-elderly patients, particularly with hemorrhagic presentation. Brain magnetic resonance imaging (MRI) plays an important role in the diagnosis of this entity, which typically demonstrates restricted diffusion and a T2 hypointense appearance, suggesting hypercellularity. CASE REPORT A 44-year-old man came to the emergency department with a persistent and treatment-resistant bilateral frontal headache that had been bothering him for the past 3 weeks. Upon conducting a neurological assessment, the patient displayed temporal disorientation and incoherent speech, but without any observable motor deficits. A non-contrast enhanced brain computed tomography scan was carried out, revealing a hyperattenuating, space-occupying lesion and hemorrhage in the left hemisphere of the brain. Subsequently, brain MRI demonstrated hypointense signal on T2-weighted images, restricted diffusion, and homogeneous lesional contrast enhancement, suggesting a very cellular expansive lesion with hemorrhage. To establish a definitive diagnosis, a brain biopsy was undertaken, confirming the presence of DLBCL of the primary central nervous system (germinal center phenotype). CONCLUSIONS Hemorrhagic presentation of primary central nervous system DLBCL occurs very rarely, particularly in non-elderly immunocompetent patients. Brain MRI plays an important role in the diagnosis of this entity, which allows differentiation from high-grade glial or other lesions that present more frequently with hemorrhage. Therefore, it is crucial to suspect lymphoma before surgical intervention for appropriate patient management.