Tanza ni a is going through profound restructuring that force the Public Sector to become more efficient and effective. In this respect, one of the most popular tools used in the contemporary reform programme is the appli cation of Open Performance Review and Appraisal System. However. the successful implementation of Open Performance Review and Appraisal System faces numerous challenges and obstacles. The study aimed in assessin g the contribution of Performance Appraisal in the Perfo rmance of different ministri es in the Govern ment. The general objective of the study is to identifying factors affecti ng the smooth implementation of OPRAS in the Ministry of Foreign Affairs and International Cooperation". Specifically the study was to examine the factors affecting the implementation of Performance Appraisal System in Ministry of Foreign AITairs ancl International Cooperation"; how Performance Appraisal System affect employees performance in the Mi nistry and suggesting the strategies for effective implementation or Performance Appraisal in the Ministry. The study employed a case study design with questionnaires. interviews, and documentation as the mai n data collection methods. This study used both Qua litati ve and Quantitati ve approaches. The study fi ndings revealed that the contribution of Performance Appraisal in Tanzania faced different challenges including financial resou rce constraints, poor participation of employees in preparation process. practicability as well as leadership style. The findin gs also, revealed that, about 18 percent of the respondents strongly agreed that Performance Appraisal change the performa nce or the employees in the min istry whil e 40.7 percent strongly disagree to the notion that performance appraisal change the performance of the employees. On the other hand. 28.J percent disagree whil e 13 percent were uncerta in . Thus, the identified challenges affect the contribution of Performance Appraisal System in the Ministry. However, the stud y suggested the strategies for better implementation of OPRAS which include clear goals and expectations, political will, monitor performance and rewa rding the right behavior.