BACKGROUND Lymphomatoid granulomatosis is a rare disorder of the central nervous system (CNS) with few cases being reported in literature. We present the case of an adult with an unusual lesion of the CNS who presented with motor seizures and was diagnosed with lymphomatoid granulomatosis, followed by a discussion of the process of evaluation and management. METHODS A 42-year-old male presented with motor seizures and loss of consciousness for 10 minutes along with dysarthria and left hemiplegia. Neurological examination and imaging with magnetic resonance imaging (MRI) of the brain revealed a mass in the right striatum. The patient was hospitalized and underwent an image-guided right frontal craniotomy using the Leksell Stereotactic G-Frame. Pathology reported a lymphomatoid granulomatosis. Being immunocompetent, the patient received medical treatment with prednisone and rituximab. Two years after his diagnosis, the patient had no active disease and his brain MRI did not show contrast enhancement. After almost 3 years of follow-up, the patient has a mild weakness in the left-side of his body (4/5), is seizure-free, and can walk and perform daily activities. CONCLUSIONS This rare lesion in an adult, immunocompetent patient, debuting with motor seizures represents a challenge in terms of diagnosis and treatment. After surgical and medical treatment, the patient had a satisfactory recovery. Clinical features, imaging, differential diagnosis, and pathology are discussed.