Abstract Objectives Hematopoietic stem cell transplantation (HSCT) can be a traumatic experience for the patient, engendering psychological distress and sometimes post-traumatic stress disorder (PTSD). The aim of this study was to explore the relations between psychological resources (i.e., dispositional mindfulness, optimism, and acceptance) and deleterious factors (i.e., experiential avoidance and alexithymia) assessed before HSCT on PTSD symptomatology 5 months after transplantation. The relations between symptoms of PTSD and the five facets of dispositional mindfulness were also explored. Methods Among the 187 patients who completed the first questionnaire measuring dispositional factors (i.e., dispositional mindfulness, acceptance, optimism, experiential avoidance, and alexithymia) prior to hospitalization, 91 patients were assessed at 5 months after HSCT on PTSD symptomatology. Various medical and mental health variables were controlled.Results Acceptance, experiential avoidance, and the non-judging facet of mindfulness correlated significantly with PTSD symptoms at 5months. Adjusting for major comorbid psychiatric disorders of PTSD (i.e., anxiety and depression), only expe-riential avoidance and mindful non-judging remained significant correlates of PTSD symptomatology. In addition, controlling for the same comorbidities, a binary logistic regression analysis revealed that only the non-judging facet of mindfulness is related to a lower risk of developing symptoms of PTSD (OR = 0.38, p < .01; 95% CI: 0.16, 0.95).Conclusions This study highlights the importance of psychological constructs barely explored in HSCT. Cultivating a state of non-judgment and non-avoidance of internal experiences is negatively associated to PTSD symptoms following HSCT.