Graft-versus-host disease (GvHD) is a common complication following haematopoietic stem cell transplant but little is published about the impact of this condition on hospital readmission rates. We report a retrospective analysis of readmission rates and associated costs in 187 consecutive allogeneic transplant patients to assess the impact of GvHD. The overall readmission rate was higher in patients with GvHD (86% (101/118) vs. 59% (41/69), p < 0.001). The readmission rate was higher both in the first 100 d from transplant (p = 0.02) and in the first year following transplant (p < 0.001). 151/455 (33%) of all readmission episodes occurred within 100 d of transplant. The mean number of inpatient days was significantly higher in patients with grade III/IV acute GvHD (101 d) compared with those with grade I/II GvHD (70 d; p = 0.003). The mean cost of readmission was higher in patients with GvHD (£28 860) than in non-GvHD patients (£13 405; p = 0.002) and in patients with grade III/IV GvHD (£40 012) compared with those patients with grade I/II GvHD (£24 560; p = 0.038). Survival was higher in those with grade I/II GvHD (55%) compared to grade III/IV GvHD (14%; p < 0.001). This study shows the high economic burden and poor overall survival associated with grade III/IV GvHD.