Abstract
<title>Abstract</title> <p> Resilience and psychological flexibility (PF) are protective factors for mental health and well-being in the general population as well as in patients with cancer. Research suggests the PF is a resilience factor and mediates the association between resilience and psychological outcomes in various contexts. However, no study investigated the mediating role of PF in the relationship between resilience and psychological outcomes in patients with cancer so far. This study examined PF and its core processes as mediators of the relationship between resilience and psychological outcomes in patients with cancer. A total of <italic>N</italic> = 218 participants completed an online survey assessing resilience (RS-11), PF (AAQ-2), distress (NCCN distress thermometer), depression (PHQ-8), anxiety (GAD-7), and mental health-related quality of life (SF-12). Across all bootstrapped mediation models, PF fully mediated the relationship between resilience and all psychological outcomes. Subanalyses of acceptance (PEACE-G) and value-based living (VQ-G) showed full mediation, with distinct association patterns for these core processes. Our findings highlight PF as a key mediator between resilience and psychological outcomes in cancer patients. Obstruction (subscale of the VQ-G) showed the strongest association, suggesting that ACT-based interventions targeting psychological barriers may be particularly effective in enhancing resilience and mental health. </p>