Background <p>National cancer treatment protocols guide drug selection, dosing, and access to care. While Australia, Canada, and the United Kingdom (UK) have similar socialised healthcare systems, the extent to which their treatment protocols align remains unclear. This study compared protocols across these countries, examining drug selection, distribution by cancer type, and dosing.</p> Methods <p>A cross-sectional analysis was conducted of in-use protocols as of January 2025 from eviQ (Australia), Cancer Care Ontario (Canada), and the Clatterbridge Cancer Centre (UK). Protocols were reviewed to identify and compare chemotherapy drugs, their cancer indications, and recommended doses.</p> Results <p>Among 243 chemotherapy drugs across 2,450 protocols, 51% (123/243) were used in all three countries and 72% (175/243) appeared in at least two. Overlap was greatest for commonly used cytotoxic agents in high-incidence cancers. Dosing practices varied: Canadian protocols often recommended higher median doses, UK protocols used narrower minimum dose ranges, and Australian protocols demonstrated wider minimum–maximum dose ranges across several drugs.</p> Conclusions <p>Despite comparable access to internationally available therapies, treatment approaches vary across Australia, Canada, and the UK. As countries that frequently participate in multinational clinical trials and operate within similar evidence-based guideline and appraisal systems, these differences highlight opportunities for greater alignment. Cross-country comparisons may support collaborative efforts in protocol development and data sharing to standardise care, particularly for rare and emerging therapies targeting smaller patient populations.</p>