Background : Physicians often prescribe original biologic products to patients who have not used them before and are reluctant to switch to biosimilars. Biosimilars are highly similar versions of already-approved biologics, but healthcare professionals typically hesitate to transition patients from the original products to biosimilars. This study aims to investigate the factors that influence U.S. healthcare professionals' intentions to use biosimilars. Methods : A cross-sectional study was conducted. 510 participants were eligible healthcare professionals (279 physicians and 231 pharmacists). The theory of planned behavior (TPB) is used to identify which factors affect healthcare professionals' intentions. Descriptive statistics, chi-square, and the logistic regression model tested the TPB constructs as predictors of intentions toward biosimilars. Results : Among 279 physicians, most were aged 61 and above, with high (n = 142) and low (n = 137) intentions. Male physicians constituted 71% of the population. Attending physicians (66.3%) showed consistent perceptions towards biosimilars, primarily in the private sector (76.3%). Pharmacists (n = 231), a higher percentage of females demonstrated higher intentions compared to males (35.5% vs. 28.1%); the majority were community pharmacists. Associations between years of practice and intentions were significant. Positive correlations existed between beliefs and intentions, except for normative beliefs. Conclusions : This study revealed diverse attitudes among healthcare professionals towards biosimilars in the USA. Pharmacists and physicians, especially those with limited experience, require ongoing education on biosimilar manufacturing pathways. This education supports the appropriate use of biosimilars and helps standardize federal and state legislation.