Much literature on teacher professionalism asserts that teacher performance could be improved through the enforcement of teacher evaluation policy; therefore, we took the task of investigating whether this assertion has much merit in a centralized education system. The school system of Oman was taken as a case. Our study largely employed the qualitative research methodology, which included cross-referencing of data elicited from document analysis, examination of evaluator reports, and interview sessions with different groups of implementers and evaluators. Our study found that policy implementation spiraled down from the top level authority and then caused a pervasive web of chain reactions at the middle and bottpri levels. It was found fclso-thdt implementers' disposition play a critical role in the dynamics of the evaluation process and in determining successful implementation of the policy. In addition, there were many challenges and constraints in carrying out the policy, but administrators and evaluators in Oman were commendable for taking a bold, positive step toward improving teacher professionalism via performance-based teacher evaluation policy. Keywords: policy Implementation process, teacher evaluation, teacher professionalism, teacher Improvement