BACKGROUND: It is unknown whether using pegfilgrastim biosimilars is cost saving in a real-world setting. OBJECTIVE: To compare medical costs including pegfilgrastim drug costs and febrile neutropenia (FN) treatment and management costs between pegfilgrastim biosimilars (pegfilgrastim-jmdb, pegfilgrastim-cbqv) and originator users for primary prophylaxis of febrile neutropenia. METHODS: A retrospective cohort study using 2019 IBM MarketScan Commercial and Medicare Supplemental databases was conducted in adult patients with cancer initiating myelosuppressive chemotherapy courses. At least 2 diagnoses of the same cancer (at least 7 days apart) were required within 30 days of the chemotherapy initiation date. Pegfilgrastim (excluding on-body injector) costs included drug costs only (excluding administration fees). FN-related costs included all FN-related health care utilizations that were defined as having neutropenia, fever, or infection diagnosis. Per-patient per-cycle (PPPC) out-of-pocket (OOP) costs, health plan costs, and total costs were compared between originator (excluding on-body injector) and biosimilars users in the first cycle. A generalized linear model and a 2-part model were used. RESULTS: A total of 1,930 patients were included, of whom 884 (45.8%) used pegfilgrastim originator, 427 (22.1%) used pegfilgrastim-jmdb, and 619 (32.1%) used pegfilgrastim-cbqv. Adjusted PPPC OOP pegfilgrastim costs in the first cycle were significantly lower for the biosimilars vs the originator ($182 for pegfilgrastim-jmdb and $159 for pegfilgrastim-cbqv vs $299 for originator, P < 0.0001 for both comparisons). However, there was no difference in health plan costs ($5,783 for pegfilgrastim-jmdb and $5,845 for pegfilgrastim-cbqv vs $5,618 for originator) and total costs. In addition, no difference was observed for adjusted PPPC FN treatment and management OOP costs, health plan costs, and total costs in the first cycle. FN treatment OOP costs were $192 for originator, $197 for pegfilgrastim-jmdb (P = 0.958), and $240 for pegfilgrastim-cbqv (P = 0.680). FN treatment health plan costs were $2,804 for originator, $2,970 for pegfilgrastim-jmdb (P = 0.692), and $2,745 for pegfilgrastim-cbqv (P = 0.879). CONCLUSIONS: In a commercially insured population, using pegfilgrastim biosimilars in the first cycle for primary prophylaxis of FN led to cost savings for patients but not payers. No difference in FN-related costs was observed.