A Dissertation Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Business Administration in Corporate Management (MBA-CM) to Mzumbe University.The study focused on the assessment of the implementation of OPRAS in Public Sector Organizations in Tanzania; a case of PO-PSM. The study covered five specific objectives which were to examine the status of implementation of OPRAS in Tanzania Public Service, to determine whether OPRASS has enhanced employees’ performance in the Public Service, to identify factors that enhance performance in Public Service, to examine existing challenges on implementing OPRAS in Tanzania Public Service and to suggest alternatives of effective implementation of OPRAS in Tanzania Public Service. Data were collected through interview, questionnaires as well as reviewing other secondary sources including reports, memos and charters. The sample size was 80 respondents. That is 20% of the 400 PO-PSM employees. This included stratified random sampling which involved 70 respondents from Staff list, and purposive sampling was used for 10 leaders to complement the perception and views pointed out by employees in the questionnaire. Findings were processed through SPSS version 16 for their interpretation and analysis so as to respond to the research. The study founded out that OPRAS has been implemented, but through its operationalization, it has not succeeded to get its intended objectives well within its organization. This is because the OPRAS is being faced with a number of challenges for instance OPRAS is based on ability to measure outputs yet it is not easy to measure outputs, some work cannot be measured, OPRAS is too time consuming to implement, Government did not stress its implementation, OPRAS is not well understood, management lack expertise on OPRAS, management does not really work to develop and improve staff performance; they simply administer employees, budget is not linked to activities and there are no safeguards against overspending and overdrawing from other people's activities., lack of specifities and lack of availability of resources both human and non-human. It is recommended that, there is a need of more training on OPRAS to its employees, availability of resources, as well as working on other motivational factors to employees. In this way OPRAS will realize the words of Eroke (2013) that, “the fundamental purpose of any performance appraisal to improve workplace performance by helping employees understand their role, to maximize their chances of success within the working environment, help plan their career, and help their organization to succeed”.