Background: Patients’ experience during HCT hospitalization leads to significant psychological distress post-HCT. Inpatient palliative care integrated with transplant care improves patient-reported QOL and symptom burden during hospitalization for HCT. We assessed the impact of the inpatient palliative care intervention on patients’ QOL, mood, and post-traumatic stress disorder (PTSD) at 6 months post-HCT. Methods: We randomized 160 patients with hematologic malignancies admitted for autologous or allogeneic HCT to an inpatient palliative care intervention (n=81) integrated with transplant care compared to transplant care alone (n=79). At baseline and 6 months post-HCT, we assessed QOL, mood, and PTSD symptoms using the Functional Assessment of Cancer Therapy-Bone Marrow Transplant (FACT-BMT), the Hospital Anxiety and Depression Scale (HADS) and Patient Health Questionnaire (PHQ-9), and the PTSD checklist, respectively. To assess symptom burden during HCT hospitalization, we used the Edmonton Symptom Assessment Scale. We utilized linear regression models controlling for baseline values to analyze the intervention effects on outcomes at 6 months. We conducted causal mediation analyses to examine whether symptom burden during HCT mediated the effect of the intervention on outcomes at 6 months. Results: Between 8/14 and 1/16, we enrolled 160/186 (86%) of potentially eligible patients. At 6 months post-HCT, the intervention led to improvements in depression and PTSD symptoms, but not QOL or anxiety [Table]. Improvement in symptom burden during HCT hospitalization partially mediated the effect of the intervention on patient-reported outcomes at six months post-HCT. Conclusions: Inpatient palliative care integrated with transplant care leads to improvements in depression and PTSD symptoms at 6 months post-HCT. Addressing symptom burden during HCT hospitalization partially accounts for the effect of the intervention on these long-term outcomes. Clinical trial information: NCT02207322