The BMT CTN 1703 phase III trial confirmed that graft-versus-host disease (GVHD) prophylaxis with post-transplantation cyclophosphamide (PTCy), tacrolimus (Tac), and mycophenolate mofetil (MMF) results in superior GVHD-free, relapse-free survival (GRFS) compared with Tac/methotrexate (MTX) prophylaxis. This companion study assesses the effect of these regimens on patient-reported outcomes (PROs). Using the Lee Chronic GVHD Symptom Score and PROMIS subscales (physical function, GI symptoms, social role satisfaction) as primary end points and hemorrhagic cystitis symptoms and Lee subscales as secondary end points, responses from English and Spanish speakers were analyzed at baseline and days 100, 180, and 365 after transplant. PRO scores were compared between the arms using inverse probability weighted-independent estimating equation models. The PTCy arm had significantly lower scores on the Lee Chronic GVHD Symptom Scale (P = .01), indicating lower GVHD symptom burden. Lee Scale nutrition and mouth subscores were also better in the PTCy arm compared with the Tac/MTX arm (P < .01 for both). Older participants (age >65 years) reported better Lee Scale psychological subscores than younger participants (P = .003). No significant differences were identified in hemorrhagic cystitis or in the PROMIS subscales between treatment arms. The updated clinical end points at 2 years for the parent trial confirmed that PTCy/Tac/MMF maintained a significant advantage over Tac/MTX in GRFS (42.4% v 28.8%, P = .001). In addition to improved GRFS, patients randomly assigned to the PTCy arm reported lower symptom burden during the first year after transplant.