Febrile neutropenia caused by chemotherapy is a frequent medical emergency associated with severe complications in the emergency department (ED). Timely administration of antibiotics is believed to improve patient outcomes for several infectious diseases such as pneumonia and sepsis but has not been thoroughly evaluated for reducing risk of complications in chemotherapy-induced febrile neutropenia. The aim of this study was to evaluate associations between the risk factors and serious complications in patients presenting to the ED with febrile neutropenia. We reviewed the health information system database to identify a retrospective cohort of patients with febrile neutropenia who visited the ED of a tertiary medical hospital from January to December 2008. Only episodes of febrile neutropenia caused by chemotherapy for underlying cancer were included. Serious complications during hospitalization were defined as unstable hemodynamic status, respiratory distress, altered mental status, newly developed arrhythmia that required intervention, and death during hospitalization. Univariate and multivariate logistic regression analysis was performed to determine potential factors associated with serious complications. We further use decision tree approach to help analyze variables. Among a total of 81 febrile neutropenic episodes in 78 patients, 25 (30.8%) episodes of serious complications were identified. Latency of the first dose of antibiotics, pneumonia and platelet counts ≤ 50,000/mm(3) were identified as independent factors associated with serious complications of febrile neutropenia. Earlier administration of antibiotics is associated with fewer complications in patients presenting to the ED with febrile neutropenia.