The integration of occupational psychology principles into human resource management is considered appropriate to increase employee productivity and the effectiveness of public sector organizations. In Greece, the use of psychological factors in human resource management in the public sector is a relatively new field, as occupational psychology has been included in the training programs of public sector executives only in recent years. In addition, the percentage of public administration executives trained in the use of psychological agents has not yet been investigated. Also, there is a lack of research evaluating the results obtained concerning the efficiency and effectiveness of the organization when managers and heads of departments apply the principles of occupational psychology. This research aims to address this existing gap. 520 Directors and heads of services of the Greek public sector answered an electronic questionnaire designed by the researcher, based on the purpose and research hypotheses they investigated: 1st to have great interest from managers in acquiring relevant knowledge and 2nd that those executives who received relevant training make intensive use of the knowledge they acquired. The electronic questionnaire was sent to all services of the Greek State and was answered by 520 directors and supervisors.The results showed that there is a high percentage of executives who are trained and use psychological factors in human resource management. At the same time, it was found that training in psychological aspects is crucial to improve the efficiency and effectiveness of organizations.