IgG4-related disease (IgG4-RD) is a systemic immune-mediated disease that typically manifests as fibro-inflammatory masses that can affect nearly any organ system. Renal involvement by IgG4-RD usually takes the form of IgG4-related tubulointerstitial nephritis, but cases of membranous glomerulonephritis (MGN) have also been described. Here we present a series of 9 patients (mean age at diagnosis 58 years) with MGN associated with IgG4-RD. All patients showed MGN on biopsy, presented with proteinuria (mean 8.3 g/day), and most had elevated serum creatinine (mean 2.2 mg/dl). Seven patients had known extrarenal involvement by IgG4-RD, with 5 patients having concurrent IgG4-related tubulointerstitial nephritis. Immunohistochemical analysis for the phospholipase A2 receptor, a marker of primary MGN, was negative in all 8 biopsies so examined. Six of 7 patients with available follow-up (mean 39 months) were treated with immunosuppressive agents; one untreated patient developed end-stage renal disease and underwent transplantation, without recurrence at 12 years after transplant. All 6 treated patients showed decreased proteinuria (mean 1.2 g/day), and most showed decreased serum creatinine (mean 1.4 mg/dl). Thus, MGN should be included in the spectrum of IgG4-RD and should be suspected in proteinuric IgG4-RD patients. Conversely, patients with MGN and an appropriate clinical history should be evaluated for IgG4-RD.