Objective: Using the Comprehensive Score for Financial Toxicity (COST) tool to measure financial toxicity (FT) among differentiated thyroid cancer (DTC) patients in China and investigate the association between FT and psychological distress. Methods: We carried out a cross-sectional investigation of individuals who had survived DTC in two tertiary medical facilities. The assessment of FT was performed using the Chinese version of the COST tool. The National Comprehensive Cancer Network (NCCN) Distress Thermometer (DT) was used to measure psychological distress. A multivariate logistic regression model was constructed to identify factors related to FT, and the Pearson correlation was used to evaluate the association between COST and DT scores. Results: Out of the 207 patients who participated in this study, the average COST score was 16.3. Notably, the prevalence of financial toxicity was 47.8% (95% CI: 41% similar to 54.7%) of the patients. Of these, 22.7% (47/207) were mild FT, 23.7% (49/207) were moderate FT, and 1.4% (3/207) were severe FT. Four variables were found to be associated with increased FT in the logistic regression model, younger age (odd ratio [OR], 4.52; p = 0.003), lower educational level [OR], 1.13; p = 0.040, uninsured (odd ratio [OR], 6.53; p = 0.028), had lower household income (odd ratio [OR], 6.34; p = 0.037), and advanced cancer (odd ratio [OR], 2.99; p = 0.034). Furthermore, the Pearson correlation revealed a mild correlation between financial toxicity and psychological distress (r = -0.53, p < 0.001). Conclusion: In this study, the prevalence of FT in DTC patients was 47.8%. FT was associated with younger age, lower educational level, uninsured, had lower household income, and advanced cancer. Clinicians should identify patients by predictors early and conduct psychological interventions.