The IgG4-related disease (IgG4-RD) is an established fibroinflammatory condition, characterised by tumefactive lesion with elevated serum IgG4 level and characteristic histopathological features. The malignant potential of IgG4- RD has been questionable. Low-grade lymphomas are commonly reported orbital malignancy that occurs in IgG4- RD. We describe a case of diffuse large B-cell lymphoma (DLBCL) associated with chronic inflammation arising within IgG4-RD of the orbit. The case highlights the association of high-grade lymphoma in chronic inflammatory condition, focussing on IgG4-RD, that is rarely documented in the orbital region, and the importance of biopsy reas- sessment in patients with longstanding and worsening proptosis.