Purpose Recent guidelines for prognostic evaluation recommend clinicians’ prediction of survival (CPS) for survival prediction in patients with advanced cancer. However, CPS is often inaccurate and optimistic. Studies on factors associated with overestimation or underestimation of CPS are limited. We aimed to investigate the factors associated with the overestimation and underestimation of CPS in patients with far-advanced cancer. Methods The current study was a secondary analysis of an international multicenter prospective cohort study, which enrolled newly admitted patients with advanced cancer in palliative care units (PCUs) in Japan, Korea, and Taiwan from 2017 to 2018. We obtained the temporal CPS at enrollment and performed multivariate logistic regression analysis to identify the factors associated with “underestimation (less than 33% of actual survival)” and “overestimation (more than 33% of actual survival).” Results A total of 2571 patients were assessed and admitted in 37 PCUs between January 2017 and September 2018. Older age (adjusted odds ratio aOR 1.01; 95% confidence interval CI 1.01–1.02; P  < 0.01) and reduced oral intake (aOR 0.68; 95% CI 0.51–0.89; P  < 0.01) were identified as significant factors associated with underestimation. Dyspnea (aOR 1.28; 95% CI 1.06–1.54; P  = 0.01) and hyperactive delirium (aOR 1.34; 95% CI 1.05–1.72; P  = 0.02) were identified as significant factors associated with overestimation. Conclusion Older age was related to underestimation, while dyspnea and hyperactive delirium were related to overestimation of CPS for patients with weeks of survival. However, reduced oral intake was less likely to lead to underestimation.