A Dissertation Submitted to Mzumbe University, Dar es salaam campus in Partial Fulfillment of the Requirements for the Award of Masters Degree of science in Human Resources Management (M.Sc. HRM)The Performance Management System (PMS) has been introduced in Tanzania public service with the intentions of monitoring, reviewing, assessing performance, developing underperformers, recognizing and rewarding good performance. The purpose of this study was to investigate the challenges facing the installation of performance Management System in Government Organization; case of President Office Public Service Management. The specific objectives included, to examine the factors associated with the installation of Performance Management system, to determine whether POPSM has developed appropriate Training programmes on Performance Management system to the Government organization, and to assess the awareness of Government organizations on Performance Management system. The study noted various challenges facing the installation of PMS as there were cases of resistance to change, some supervisors negotiated for easy targets than their ability. Moreover the study revealed that; lack of good information system on PMS and lack of acceptance of OPRAS form to most of the supporting staff have also caused challenges of installation of PMS. The study recommended that; there should be a regular and thorough training of officials within the Government Organizations about the PMS and how it influences productivity, the Departmental Moderating Committee (OPRAS committee) should demand verifiable evidence to justify a higher rating during quarterly assessments, and that punitive/disciplinary measures be taken against those who do not comply with the provision of the PMS policy, particularly failure to submit performance instruments. the organization’s management should try and encourage the workers who are still opposed to the issue of performance management system on its benefits to the organization, the organization should roll out performance Management systems to other levels in the hierarchy of management and the organization should also move with speed and have its workers undergo training and university education, up from the tertiary level. Other findings of the study include that there is a challenge of biased ratings (subjective assessment), and a setting of unrealistic performance targets which are unrealizable by employees. The foregoing justifies the reasons why productivity levels are not always realized and targets not achieved by the Government organization.