The third international consensus definition of sepsis (Sepsis-3) recommends the quick sequential organ failure assessment (qSOFA) screening tool in patients with suspected infection. The Early Warning Score (EWS) helps to estimate mortality risk in emergency patients. The National EWS (NEWS) is a bedside score of six routine vital parameters. Few studies have compared qSOFA and NEWS in detecting suspected sepsis in cancer patients, so we compared them as a Sepsis-3 prognostic tool. [Methods] This is a retrospective observational single-center study. The study population consisted of cancer patients who entered the intensive care unit (ICU) between 2014 and 2016 for Sepsis-1 (based on systemic inflammatory response syndrome [SIRS] criteria). We calculated and compared the sensitivity and specificity of qSOFA and NEWS. We performed a receiver operating characteristic (ROC) curve analysis of NEWS in the diagnosis of Sepsis-3. [Results] Of the 62 patients admitted to the ICU for Sepsis-1, 42 had Sepsis-3. For qSOFA, sensitivity was 0.71 and specificity was 0.75. Exploratory analysis using the Youden index suggested that 9 may be the optimal score for NEWS. The sensitivity and specificity of NEWS at 9 points were 0.81 and 0.95, respectively. [Conclusion] We found NEWS to be more accurate than qSOFA in screening for epsis-3.