To estimate the cost of first-line treatment in patients with PTCL, from the government payer perspective, in France, Germany, and the UK A cost calculator was designed to apply country-specific unit costs to treatments and other healthcare resource use collected in a retrospective medical chart review study conducted in France, Germany, and the UK. The study included PTCL patients diagnosed between January 1, 2014 and December 31, 2016, who received at least front-line treatment for PTCL. Medical chart data, including PTCL treatments, adjunctive therapies (e.g., antibiotics, antivirals, granulocyte-colony stimulating factor), radiotherapy, laboratory tests, inpatient and outpatient visits, and ancillary care, were collected. Unit costs for each type of resource used were sourced from tariffs in each country, and adjusted to 2020 values. Resource use was then multiplied by the corresponding unit cost to calculate the total cost by resource type, and the mean cost per patient was calculated. Results were stratified by country, PTCL subtype, front-line treatment regimen, age, and receipt of stem cell transplant. Data for a total of 165 patients (France, 53; Germany, 56; UK, 56) were collected in the chart review. The median age at diagnosis was 62 years, 81% of patients had an ECOG status of 0-1 at diagnosis, and 72% had stage III/IV disease. Total costs of first-line therapy were €12,257 per patient in France, €22,392 in Germany, and €32,461 in the UK. The greatest proportion of costs was attributed to adjunctive therapies in France (€4,509) and Germany (€11,539), and stem cell transplant in the UK (€13,419). Of note, patients in the UK were more likely to have received a stem cell transplant (44.6%) compared to France (13.2%) and Germany (19.6%). Adjunctive therapies and stem cell transplants are major cost drivers in patients with PTCL receiving front-line treatment.