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Filgrastim, a biopharmaceutical listed on WHO model list of essential medicines, was approved in USA in 1991 for patients with non-myeloid malignancies associated with severe neutropenia and fever. Several filgrastim biosimilars have now been approved in USA, Europe and elsewhere since 2008, based on the reference product which has lost patent exclusivity; however their immunogenicity and safety is controversial. We conducted a retrospective, post market study between 1991 and May 2018 using VigiBase®. The study included all adverse events with case reports ≥150. Overall, 11,183 adverse drugs reaction reports were identified during observation period; of which 5764; 51.5% reports concerned to Neupogen®, the originator, and rest consists of Leucostim® (N = 680), Zarzio® (N = 622), Grasin® (N = 545), Nivestim® (N = 359) and Tevagrastim® (N = 152) biosimilars. When compared with the originator, Grasin® was associated with higher reporting of pyrexia (11.5% vs 7.9%, ROR 1.52, IC025 1.12), myalgia (37% vs 2.2%, ROR 25.94, IC025 2.11) and back pain (11.3% vs 4%, ROR 3.09, IC025 2.32). Zarzio® was associated with increased reporting of arthralgia (4.5% vs 2.9%, ROR 1.59, IC025 1.25) and neutropenia (11.4% vs 4%, ROR 2.59, IC025 3.07). Bone pain was reported more often with Nivestim® (14.4% vs 8.3%, ROR 1.87, IC025 5.30). Drug ineffectiveness was reported in cases with Zarzio® (35.9%), Nivestim® (19.4%) and Tevagrastim® (42.2%). Authors observed significant differences among originator and biosimilars in particular to efficacy, adverse events reported and time to onset of occurrences. Large epidemiologic studies are needed to further confirm these finding and provide additional insights.Filgrastim is a recombinant human granulocyte-colony stimulating factor protein.Filgrastim is approved to treat febrile neutropenia associated with non-myeloid malignancies.Presently, several biosimilars claiming equivalent to filgrastim originator licensed worldwide.VigiBase®, a WHO global database of individual case safety reports is used for post-market study.Significant differences in safety profiles among originator and biosimilars are observed.