AIMS: We aimed to investigate the impact of interleukin (IL)-34 and YKL-40, regulators of hepatic fibrosis and tumor growth, on the prognosis of patients with non-viral hepatocellular carcinoma (HCC). METHODS: We enrolled 159 non-viral HCC patients (age, 70.8 ± 8.5 years; female/male, 43/116). Of these, 86 patients were alive and 73 patients had died at the censor time point. Serum IL-34 and YKL-40 levels were quantified by enzyme-linked immunosorbent assay. Patients were stratified by the median level of serum IL-34 to examine its effect on survival. Multivariate analysis and random forest analysis were used to evaluate the impact of IL-34 and YKL-40 on the prognosis of non-viral HCC patients. RESULTS: Interleukin-34 (hazard ratio [HR] 1.30; 95% confidence interval [CI], 1.13-1.49; P ≤ 0.01), tumor size (HR 1.63; 95% CI, 1.37-1.94; P ≤ 0.01), and tumor number (HR 1.53; 95% CI, 1.25-1.87; P ≤ 0.01) were independent predictive factors for survival. Furthermore, the survival rates were significantly lower in the high IL-34 group than in the low IL-34 group (5-year survival rates, 34.7% vs. 59.8%, respectively; P < 0.05). In the random forest analysis for survival, IL-34 was the third-highest ranking factor, following tumor size and number. In a stratification analysis, serum α-fetoprotein level and Fibrosis-4 index were independent positive risk factors for high serum IL-34 level. YKL-40 was not associated with prognosis in either the multivariate or random forest analysis. CONCLUSION: Interleukin-34 was an independent factor for survival of non-viral HCC patients. Interleukin-34 might be associated with prognosis through tumor and hepatic fibrosis factors.