The paper reviews motives, nature and theoretical philosophy along the adoption and implementation stages of New Public Management (NPM) - accounting reforms in the Public sector of developing countries. The paper finds the main motive along the stage of adoption and implementation of NPM accounting reforms is characterized with an aspect of gain legitimacy of accessing the financial support from donors of different levels who create coercive and normative pressure of increasing efficiency in public sector operations. Among others the nature of NPM reforms which undertaken by public sector of developing countries is mostly focused to the accounting and at most accrual accounting systems. The theoretical philosophy pertains the adoption and implementation of NPM reforms in the sector is focused on New institutional theory which argues that adoption and implementation is contributing more by external environment pressures with coercive, normative and mimeticmechanisms; in which public sector of developing country organizations tend to respond them in order to gain financial resources. This resulted intoo little internal efficiency due to manipulation and loose coupling practices by the public sector actors in daily operations. Therefore, in order to effectuate implementation and success of the practices of NPM accounting reforms in the developing country public sectors, the adoption motive should be developed from internal structure and demand for efficiency with political will and coexisting of pressure from both internal and external institutionalized environments.