Homeobox A9 promoter methylation (HOXA9) has been reported as a biomarker for early lung adenocarcinoma patients' prognosis. We aim to evaluate its prognostic value, regardless of disease stage. Using droplet digital PCR, we measured HOXA9 methylation in a cohort comprising 161 Brazilian patients. Low HOXA9 methylation was associated with higher cancer-specific survival but showed no significance after adjustment for clinical covariates. While low HOXA9 methylation was associated with earlier stages, no survival association was observed in this subset of patients. Overall, HOXA9 promoter methylation is not an independent prognostic biomarker of cancer-specific survival in Brazilian lung adenocarcinomas patients.