Aim: In the study, an evaluation was made by using Robert K. Merton's theory of 'Unexpected Effects of Purposeful Social Actions' and it was thought that unexpected effects might occur as well as expected results. In this sense, it is aimed to reveal the unexpected effects of the performance-based supplementary payment system on health workers. Method: Qualitative research design was used in the study. The data of the study were obtained by semi-structured interview method with the participation of 18 nurses and six physicians working in a public and university hospital. Results: Two main themes and seven sub-themes emerged in the study. The first theme is solution options for quota problems and consists of three sub-themes: borrowing, complaint, and acceptance. The second theme is the number of patients receiving care and service-quality balance, and its sub-themes are excessive workload, patient satisfaction, caring for quality, and conscientiousness. Conclusion: There are criticisms of the performance-based supplementary payment system on the basis of existing health policies. In this study, in which the effects of the mentioned situation on healthcare professionals were examined, it was concluded that the system was insufficient in terms of both ethics and payments.