Our aim was to compare the efficacy and safety of two recently developed biosimilars of pegfilgrastim, a pegylated form of the recombinant human granulocyte‐colony stimulating factor (G‐CSF) analog filgrastim with those of the reference pegfilgrastim. We retrospectively analyzed data from patients diagnosed with diffuse large B‐cell lymphoma (DLBCL) who were treated with first‐line R‐CHOP chemotherapy and received pegylated G‐CSF for primary prophylaxis. The following pegylated G‐CSFs were analyzed in this study: reference pegfilgrastim (Neulasta^®) and two of its biosimilars (tripegfilgrastim; Dulastin^® and pegteograstim; Neulapeg^®). In total, 296 patients were enrolled. The number of patients with at least one episode of neutropenia during R‐CHOP chemotherapy was the lowest in the reference cohort (pegfilgrastim: 127 of 193 patients, 65.8%; tripegfilgrastim: 64 of 69 patients, 92.8%; pegteograstim: 28 of 34 patients, 82.4%, P < .001). The number of patients with at least one episode of febrile neutropenia was also lowest in the reference cohort (pegfilgrastim: 67 of 193 patients, 34.7%; tripegfilgrastim: 38 of 69 patients, 55.1%; pegteograstim: 16 of 34 patients, 47.1%, P = .009). There were no differences in the duration of neutropenia and febrile neutropenia or treatment outcomes (rate of complete response or relapse and survival). There were no reports of grade 3 or higher adverse events requiring discontinuation of prophylactic pegylated G‐CSF in any group. The safety of the pegfilgrastim biosimilars for prophylactic purposes was comparable to that of the reference pegfilgrastim; however, in terms of their efficacy, the incidence of neutropenia and febrile neutropenia tended to be higher than that when using pegfilgrastim. The clinical relevance of these results in the biosimilar cohorts should be explored.