This systematic review examines the barriers to adopting a plant-based diet (PBD) among adults aged 18 to 65 in high-income countries (HICs). The review mapped these barriers to behavior change strategies using the COM-B model. Ten studies, including 1740 participants, were included. Fourteen barriers were identified and synthesized into 11 themes: financial, lack of knowledge, emotional, health, convenience, social, enjoyment of meat, environmental, accessibility, personal ability, and media. Nutritional intake/requirements had the most evidence, followed by habits and lack of knowledge. Education interventions and communication/marketing policies are recommended to address these barriers. The review highlights the need for more information and education to help individuals adopt PBDs, particularly regarding nutritional requirements and the benefits of plant-based diets.This systematic review examines the barriers to adopting a plant-based diet (PBD) among adults aged 18 to 65 in high-income countries (HICs). The review mapped these barriers to behavior change strategies using the COM-B model. Ten studies, including 1740 participants, were included. Fourteen barriers were identified and synthesized into 11 themes: financial, lack of knowledge, emotional, health, convenience, social, enjoyment of meat, environmental, accessibility, personal ability, and media. Nutritional intake/requirements had the most evidence, followed by habits and lack of knowledge. Education interventions and communication/marketing policies are recommended to address these barriers. The review highlights the need for more information and education to help individuals adopt PBDs, particularly regarding nutritional requirements and the benefits of plant-based diets.