Hematopoietic stem cell transplantation (HCT) is associated with a high risk of morbidity, making advance care planning (ACP) essential. The purpose of this study was to assess and compare proxy and HCT candidate distress levels (Distress Thermometer) before (T1) and after (T2) ACP question completion. 79 participants (40 HCT candidates, 39 proxies) rated their distress. The T1, T2 mean distress scores (SD) for HCT candidates were 3.13(2.27), 2.96(2.10); 43% and 38% endorsed clinically significant distress (≥4). Proxies reported 4.21(2.48), 4.33 (2.46); 62% endorsed significant distress at T1, T2. The majority of proxies endorsed distress levels that were clinically significant and comparatively higher (T1 (p = 0.047) and T2 (p = 0.009)) than their paired HCT recipients. Responding to questions about ACP did not increase overall distress ratings.