The ideal stem cell graft source remains unknown in haploidentical haematopietic cell transplantation (haplo-HCT) with posttransplantation cyclophosphamide (PTCy). This study compared outcomes of bone marrow (BM) versus peripheral blood (PB) stem cell graft for haplo-HCT in acute lymphoblastic leukemia (ALL). A total of 314 patients with ALL (BM-157; PB-157) were included in this study. The cumulative incidence of engraftment at day 30 was higher in the PB group compared with BM (93% vs. 88%, p < 0.01). The incidences of acute graft-versus-host disease (GVHD) and chronic GVHD were not significantly different between the study cohorts. In the multivariate analysis, there were tendencies toward a higher incidence of grade II-IV acute GVHD (hazard ratio (HR) = 1.52, p = 0.07), chronic GVHD (HR = 1.58, p = 0.05), and nonrelapse mortality (NRM) (HR = 1.66, p = 0.06) in patients receiving PB versus BM graft, respectively. The use of PB grafts was associated with lower leukemia-free survival (LFS) (HR = 1.43, p = 0.05), overall survival (OS) (HR = 1.59, p = 0.02), and GVHD-free, relapse-free survival (GRFS) (HR = 1.42, p = 0.03) compared with BM grafts. There was no difference in relapse incidence (HR = 1.23, p = 0.41) between the study groups. In conclusion, use of BM graft results in better survival after haplo-HCT with PTCy in patients with ALL, compared with PB stem cell graft.