Background: IgG4-related disease (IgG4-RD) is an immune-mediated, fibroinflammatory disease affecting multiple organs. Its prevalence is estimated at 4.6 per 100,000, but accurate estimation is challenging due to limited studies with varying diagnostic criteria. Histologically, IgG4-RD is characterized by IgG4-bearing plasmocyte infiltration, storiform fibrosis, and obliterative phlebitis. Ophthalmic manifestations are common, while neurologic involvement is rare, often due to hypertrophic pachymeningitis or hypophysitis. Case Description: A 58-year-old man with controlled hypertension and recent cataract surgery presented blurry vision and headaches. Ophthalmic exam revealed left eye proptosis, limited gaze, scotoma, and hyporeactive pupil. Imaging showed intraorbital infiltrating lesions and thickened meninges. Serum analysis revealed elevated IgG4 levels. Biopsy confirmed IgG4-RD with elevated IgG4+ cells and IgG4/IgG ratio. Treatment involved oral prednisone and rituximab, resulting in improved visual acuity and symptoms. Conclusions: This case highlights several key aspects of IgG4-RD. Prompt diagnosis is vital as its symptoms overlap with other conditions like lymphoma. Histopathological examination remains crucial for definitive diagnosis. Imaging aids in recognition and differentiation, guiding appropriate treatment. Rituximab, alongside prednisone, should be considered early due to potential neuronal involvement. IgG4-RD’s diverse manifestations emphasize the need for comprehensive classification criteria. This case underscores the importance of understanding this disease’s presentation, diagnostic methods, and tailored treatment strategies to optimize patient outcomes.