Abstract The rapid emergence of expensive anticancer therapies is leading to exponential growth in healthcare expenses. In clinical trials, most investigational drugs are provided free of charge by industrial and academic sponsors. This results in drug cost savings for healthcare payers, who are no longer charged with the cost of the standard‐of‐care treatment, which would have been administered outside the trial. This study aims to estimate drug cost savings resulting from patient enrolment in hematological oncology clinical trials, from a public payer perspective. Retrospective screening identified all patients with hematological malignancies included from 2011 to 2016 in a phase III trial and having received at least one sponsor‐provided cycle. Drug cost savings were defined as the standard treatment costs not charged to the payer due to sponsor provision of treatment. For each patient, cost savings were determined by the number of cycles received in the trial and the cost of standard (control arm) treatment. Of the 345 patients included in eligible trials during study period, 272 received sponsor‐provided drugs. Drug cost savings could be estimated for 177 patients (65.1%) included in 27 trials. Total cost savings were €5218 million (US$ 6804 million) for 1720 sponsor‐provided cycles. Mean cost saving per patient was €19 182.7 ± 29 865.7 ($25 015.24 ± 39 478.25). Most cost‐saving trials were industry‐sponsored (77.8%), although academic trials generated 40.15% of total cost savings. Enrolling patients in clinical trials, whether industry‐sponsored or academic, leads to substantial drug cost savings for payers. Implications are significant for public payers facing increasing financial constraints, as savings can be reallocated to patient care.