Objective: This study explores whether cancer patients’ dysfunctional self-focus is a significant contributor to their fear of progression. In addition, we investigated whether their psychiatric symptoms such as depression, anxiety, and dysfunctional beliefs about sleep may mediate the relationship between these factors. Methods: We conducted a retrospective medical records review of 196 cancer patients who visited the Stress Management Clinic for the first time from March to September 2022. Their demographic information and responses to rating scales such as the Fear of Progression Questionnaire-Short Form (FoP-Q-SF), Dysfunctional Self-focus Attribution Scale (DSAS), Patient Health Questionnaire-9 Items (PHQ-9), State subcategory of the State and Trait of Anxiety Inventory (STAI-S), Insomnia Severity Index (ISI), Cancer-related Dysfunctional Beliefs about Sleep scale (C-DBS), and numeric rating scales of pain and fatigue were collected. Results: A high FoP-Q-SF score was significantly correlated with high PHQ-9 (r=0.60), STAI-S (r=0.38), ISI (r=0.34), C-DBS (r=0.47), pain (r=0.24), fatigue (r=0.37), and DSAS (r=0.58, all p<0.001). A linear regression analysis showed that the FoP-Q-SF score was significantly predicted by younger age (β=-0.13, p=0.011), PHQ-9 (β=0.36, p<0.001), STAI-S (β=0.18, p=0.001), C-DBS (β=0.22, p<0.001), and DSAS (β=0.25, p<0.001). A mediation analysis showed that dysfunctional self-focus directly influenced patients’ fear of progression. In addition, cancer patients’ depression, anxiety, and cancer-related dysfunctional beliefs about sleep mediated this relationship. Conclusion We observed that dysfunctional self-focus may influence cancer patients’ fear of progression, mediated by depression, anxiety, and cancer-related dysfunctional beliefs about sleep.