© 2019 Author (s) (or their employer(s)). Background Biosimilars can potentially improve the sustainability of cancer care; however, uptake is sometimes limited by safety concerns and a lack of understanding of the concept of extrapolation. The European Society for Medical Oncology (ESMO) conducted a survey to assess the current level of knowledge, understanding and comfort of use of biosimilars among prescribers specialised in oncology. Methods A 19-question survey was developed using the SurveyMonkey online platform (https://www.surveymonkey.com/). Data collection occurred between September and October 2017 and included paper and online responses. Results Overall, 393 responses were received from prescribers. Overall, 49.0% of prescribers use biosimilars in clinical practice and most (79.2%) rate their general knowledge of biosimilars as average to very high. Potential increased risk of immunogenicity remains a significant concern of switching. Gaps in knowledge identified by the survey include biosimilar development, clinical trial design and endpoint selection, and requirements for extrapolation, which should form the focus of future educational initiatives. A substantial demand remains for further educational activities with equal preference for online and face-to-face initiatives. A higher rate of biosimilar use (56.3% vs 46.5%), knowledge of biosimilar development and trial design, and comfort with extrapolation, but a lower knowledge of European Medicines Agency definitions, was found among prescribers from Asia-Pacific versus those from Europe. Conclusion Encouraging levels of prescriber use and general knowledge of biosimilars were found, but a substantial need for further education remains. Efforts should be made worldwide to align terms, definitions and guidelines for the development and approval of biosimilars.