During revision total shoulder arthroplasty, bone grafting severe glenoid defects without concomitant reinsertion of a glenoid prosthesis may be the only viable reconstructive option. However, the fate of these grafts is unknown. We questioned the durability and subsidence of the graft and the associated clinical outcomes in patients who have this procedure. We retrospectively reviewed 11 patients with severe glenoid deficiencies from aseptic loosening of a glenoid component who underwent conversion of a total shoulder arthroplasty to a humeral head replacement and glenoid bone grafting. Large cavitary defects were grafted with either allograft cancellous chips or bulk structural allograft, depending on the presence or absence of glenoid vault wall defects, without prosthetic glenoid resurfacing. Clinical outcomes (Penn Shoulder Score, maximum 100 points) improved from 23 to 57 at a minimum 2-year followup (mean, 38 months; range, 24–73 months). However, we observed substantial graft subsidence in all patients, with eight of 11 patients having subsidence greater than 5 mm; the magnitude of graft resorption did not correlate with clinical outcome scores. Greater subsidence was seen with structural than cancellous chip allografts. Bone grafting large glenoid defects during revision shoulder arthroplasty can improve clinical outcome scores, but the substantial resorption of the graft material remains a concern.