Neutrophils are the most abundant myeloid-derived eukaryotic cells in human blood with increasingly recognized as important regulators of cancer progression. However, the functional importance of tumor-associated neutrophils (TANs) is often overlooked due to their short-lived, terminally differentiated, non-proliferative properties. In recent years, a wealth of evidences obtained from experimental tumor models and cancer patients had indicated that TANs had obvious heterogeneity in morphology and function, and TANs had dual functions of pro- and anti-tumor in cancer patients. This review provides an adequate overview of the heterogeneity and distinct roles of neutrophils.