Introduction To evaluate biosimilar understanding and preference trends of medical oncologists in Turkey. Methods A survey consisting of 24 multiple-choice questions with checkbox answers was conducted among medical oncologists. The questionnaire was divided into five parts to some intentions: demographic characteristics, general knowledge about biosimilars, knowledge about local approval and reimbursement issues, individual preference trends, and ranking the knowledge of their own. All answers were analyzed as whole cohort, specialists and fellows. Results Fellows (n = 47) consisted 42%, and academic clinicians (n = 37) consisted 35% of the participants. In the whole cohort, the overall rate of correct answers was 55.1% in the general knowledge about the biosimilars part, and 26.7% in the local approval and reimbursement issues part. At all, 57.7% of the participants declared that they object to switch from a reference product to a biosimilar product. The rate of those who defined themselves as extremely knowledgeable decreased from 8.1% to 2.7% in the whole cohort at the end of the survey. Conclusion The need for more accurate and clarified local regulations and education emerging in the biotechnology era must be met.