The aim of this research is to examine and compare the shifting relationships between third sector organizations and local government under the current public service reforms in Japan and the UK. In both cases, institutional isomorphic tendency amongst third sector organizations can be found. However, in the case of UK, more formalized partnership frameworks set by central government as well as contractual relationships has an impact on this tendency. Contrastingly, Japan partnerships tend to be individualized. In this regard, the contracting framework seems to have more impact on behavior of the third sector organizations than partnership frameworks. In addition, the aspect of co-governance of the third sector organizations has been less developed than in the third sector in the UK. This affinity seems to be associated with the lack of sense of identity as a sector and also the lack of strong third sector organizations.