Background: Patients’ perceptions of their illness are important for treatment decision-making and quality of life. Limited data exist describing associations of illness perceptions with other patient-centered outcomes, particularly in CCT participants. We sought to examine associations among illness perceptions and CCT patients’ financial toxicity, physical and psychological symptoms, and survival. Methods: From 7/2015-7/2017, we prospectively enrolled CCT participants who expressed interest in financial assistance programs (n = 157) and a group of patients matched by age, sex, cancer type, specific trial, and trial phase (n = 103). We assessed baseline illness perceptions (Brief Illness Perceptions Questionnaire [BIPQ] with scores > 50 indicating negative perceptions), financial toxicity (degree costs of cancer care have been a burden, moderate to catastrophic indicating financial toxicity), physical (Edmonton Symptom Assessment Scale [ESAS]) and psychological (Patient Health Questionnaire-4 [PHQ-4]) symptoms. We used descriptive statistics to examine associations of BIPQ and sociodemographic/clinical factors, financial toxicity, ESAS, PHQ-4, and overall survival. We used the Kaplan-Meier method to estimate median survival times and Cox regression to assess the association of BIPQ and overall survival. Results: Among 260 patients, 189 (72.7%) completed BIPQ surveys (median age 69 [Range 26 to 83] years, 66.1% female). 68.8% had negative illness perceptions. We found no significant associations among negative illness perceptions and patients’ age, sex, race, education, marital status, performance status, insurance, cancer type, metastatic disease status, self-reported income, trial phase, trial year, or Charlson Comorbidity Index score. Patients with negative illness perceptions were more likely to report financial toxicity (69.8% vs 48.8%, p = 0.006), and had higher ESAS-total (Medians: 44 [Range 0-89] vs 21 [Range 0-78], p < 0.001), PHQ-4 depression (Medians: 2 [Range 0-6] vs 0 [Range 0-6], p < 0.001), and PHQ-4 anxiety (Medians: 3 [Range 0-6] vs 1 [Range 0-6], p < 0.001) scores. Patients with negative illness perceptions had shorter overall survival (Medians: 22 [Range 10-29] vs 42 [Range 28-Not Reached] months, log-rank p = 0.004). Adjusting for receipt of financial assistance, patients with negative illness perceptions experienced higher risk of death (HR 1.65, 95% CI 1.10-2.48). Conclusions: In this prospective study of CCT participants, we found that patients with negative illness perceptions experienced greater financial toxicity, more symptom burden, and worse survival than those with more positive perceptions, despite comparable sociodemographic/clinical factors. These findings highlight the need to assess and address patients’ illness perceptions and financial burden when seeking to enhance patient-centered outcomes in oncology.