Although socioeconomic factors are important determinants of population mortality, the effect of educational level on the survival of patients with cancer in China is unclear. This study aimed to assess whether educational level is associated with the prognosis of patients with cancer and to explore the mediators of this association.This multicentre cohort study included 18,251 patients diagnosed with cancer between May 2013 and December 2018. The main parameters measured were overall survival (OS) and all-cause mortality. The relationship between educational level and all-cause mortality was assessed using multifactor-corrected Cox survival analysis. Logistic regression was used to analyze the association between educational level and patient-generated subjective global assessment (PG-SGA).The mean age of the 18,251 participants (men, 9939 [54.4%]) was 57.37 ± 11.66 years. Multifactorial survival analysis showed that patients survived longer with increasing education (university and above vs. elementary school and below; p = p = <0.001, HR = 0.84, 95% CI: 0.77-0.92), and the differences were statistically significant in different subgroups. The potential impact factors included sex, age, TNM stage, and PG-SGA score. Logistic regression showed a significant negative association between educational level and the modifiable factor PG-SGA (secondary vs. primary and below; p = 0.004, HR = 0.90, 95% CI: 0.83-0.97; university and above vs. primary and below; p < 0.001, HR = 0.79, 95% CI: 0.71-0.88).Educational level was a significant prognostic factor for patients with cancer, independent of other known prognostic factors. This association was further improved by modifying the nutritional status.© 2024 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.