Introduction: The attitudes of healthcare providers towards people with mental illness have caused significant concern for the research community. Aim: The purpose of this systematic review was to examine the literature on the attitudes of healthcare professionals working in primary care settings towards people with mental illness. Methodology: A systematic search was conducted in the PubMed database, focusing on cross-sectional articles published between 2017 and 2024. The search used the concepts of ‘healthcare professionals’, ‘primary health care’, ‘attitudes’, ‘stigma’, and ‘mental illness’. Articles that met the inclusion and exclusion criteria were summarized. Results: A total of 214 studies were identified in the initial search, with 12 studies included in the final review. Eleven of the 12 studies were conducted in Asia, the Middle East, South America, and Africa, and one study in Europe. Negative attitudes towards people with mental illness were a common finding among primary healthcare professionals in these studies. Contributing factors included low educational levels, older age, cultural influences, personal contact with people with mental illness, and insufficient mental health training. Educational and training interventions were recommended in all studies to improve these attitudes. Conclusions: Healthcare professionals working in primary care often hold negative attitudes towards people with mental illness. The need for further education and training for healthcare professionals should be comprehensively addressed in future research.