Chemotherapy-induced neutropenia is commonly encountered in clinical practice. The management of neutropenia has been evolving from short-acting granulocyte colony-stimulating factors (G-CSFs) to long-acting G-CSFs. However, an evaluation of the safety and effectiveness of long-acting G-CSFs in clinical practice is still lacking.This multicenter, non-interventional study was aimed at exploring the safety and effectiveness of mecapegfilgrastim in different cancer patients in China. All patients provided written informed consent prior to the study and were treated according to routine clinical practice. Different prophylactic strategies (primary or secondary prophylaxis) were also compared.This study included 638 patients from May 2019 to November 2020. More than half of the participants were breast cancer patients. The mean age of all the patients was 56 years. White blood cell increase (6.2%) was the most frequently reported adverse event (AE) possibly related to the study drug. No unexpected AEs were reported. Grade ≥3 neutropenia in chemotherapy treatment cycle 1 was reported in 36 (5.6%) patients. Incidence of grade ≥3 neutropenia in cycle 1 in the primary and secondary prophylaxis subgroups were of 4.3% and 9.2%, respectively. A decreasing trend of severe neutropenia incidence was observed from cycle 1 to cycle 4.Mecapegfilgrastim was generally well tolerated, and no unexpected AEs were observed in this study. Primary administration of mecapegfilgrastim led to a lower incidence of neutropenia than did secondary administration. Continuous administration of mecapegfilgrastim could keep the incidence of neutropenia to a relatively low level.2021 Annals of Translational Medicine. All rights reserved.