Purpose: To evaluate the knowledge, opinions and prescribing attitudes of physicians working in an university hospital about biosimilar drugs and analyse the factors affect these parameters. Methods: In this descriptive, cross-sectional study, data was collected using a questionnaire consisting of 5 sections and 41 questions evaluating the knowledge, opinions and prescribing attitudes of physicians about biosimilar drugs. Descriptive statistics was used to report the findings; relationship between dependent and independent variables were examined using the t-test for parametric data, and Mann Whitney U and Kruskall Wallis analysis for nonparametric data. P <0.05 was considered statistically significant. Results: Questionnaire response rate was 61.9% (n=114). Physicians mean knowledge score about biosimilar drugs was 7.6 ± 2.5 out of 14 points. Have heard the concept the biosimilar drug, had training towards biosimilar drugs and high academic level were increased the mean knowledge score. Of the respondents, 45.2% of the physicians stated that biosimilar drugs are not as effective as biological reference drugs, and 35.9% thought that they aren't safe. More than half of the physicians (56.6%) stated that they did not hesitate to prescribe biosimilar drugs. Conclusions: Physicians' general knowledge level on biosimilar drugs was low and they had doubts about the efficacy and safety of biosimilar drugs. This might be related with lack of knowledge. Therefore structured training programmes related in this area, might increase the knowledge level and might positively affect physicians' opinions and attitudes on biosimilar drugs