AIM: Several recent studies have suggested that assessing heart rate variability (HRV) is an easy method for obtaining prognostic information on cancer patients; however, these studies had limitations such as uncontrolled confounders and small numbers in a heterogeneous group. The intention of our study was to explore and validate the role of HRV variables in patients with advanced non-small-cell lung cancer (NSCLC). METHOD: A total of 167 patients who were eligible for HRV testing were consecutively enrolled from a regional hospital in South Korea. Demographic and clinical variables, including the Eastern Cooperative Oncology Group (ECOG) performance status grade, NSCLC stage, therapeutic intervention, and other data were also recorded. The effects of time-domain and frequency-domain indices of HRV were compared with other clinical factors to determine overall survival. RESULTS: Among the HRV parameters, standard deviation of all normal-to-normal intervals (SDNN) significantly predicted poor survival by univariate analysis. However, multivariate analysis revealed that it was not an independent prognosticator for survival in NSCLC patients, as the HRV parameters significantly correlated with the ECOG performance status grade. CONCLUSION: HRV variables should be used to monitor advanced NSCLC patients\' general well-being and ability to perform the activities of daily living rather than to predict their overall survival.