Multiple myeloma (MM) is the main indication for autologous stem cell transplantation (ASCT). Novel supportive therapies (e.g., granulocyte colony-stimulating factor) have significantly improved post-ASCT-related mortality; however, data on biosimilar pegfilgrastim-bmez (BIO/PEG) in this setting is lacking. This prospective cohort study compared Italian patients with MM who received BIO/PEG post-ASCT with data collected retrospectively from historical control groups from the same center who received either filgrastim-sndz (BIO/G-CSF) or pegfilgrastim (PEG; originator). The primary endpoint was time to neutrophil engraftment (three consecutive days with an absolute neutrophil count ≥ 0.5 × 109/L). Secondary endpoints included incidence and duration of febrile neutropenia (FN). Of the 231 patients included, 73 were treated with PEG, 102 with BIO/G-CSF, and 56 with BIO/PEG. Median age was 60 years and 57.1% were male. Neutrophil engraftment was reached after a median of 10 days in the BIO/PEG and PEG groups and 11 days in the BIO/G-CSF group. Among patients who achieved neutrophil engraftment earlier than this (i.e., day 9), 58% (29/50) were on PEG; of those who achieved it later (i.e., day 11), 80.8% (59/73) were on BIO/G-CSF. FN incidence was higher with BIO/G-CSF (61.4%) versus PEG (52.1%) or BIO/PEG (37.5%) (p= 0.02 among groups). Patients on BIO/PEG had less frequent grade 2–3 diarrhea (5.5%) compared with BIO/G-CSF (22.5%) or PEG (21.9%); grade 2–3 mucositis was most frequent in the BIO/G-CSF group. In conclusion, pegfilgrastim and its biosimilar displayed an advantageous efficacy and safety profile compared with biosimilar filgrastim in patients with MM post-ASCT.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00277-023-05228-z.