The purpose of this doctoral dissertation is the extensive investigation of the relationship between the State and the Third sector in the fight against poverty and social exclusion. We aim to evaluate the work of NGOs, but not under the framework of a “corporate like evaluation", something that has already happened to some extent, but under a framework of macroeconomic analysis and contribution to the economy. We attempt to explore in depth the role of the State in the fight against poverty and social exclusion but also its relationship with NGOs regarding social policy on these important and troubling problems. The period 2000-2020 has been chosen to be examined, as this period best pictures the development of NGOs in Greece while also incorporating the influences of the devastating international financial crisis of 2008. The main final added value of the dissertation is to fill a significant gap in the Greek and international literature and to provide applicable policies to address poverty and social exclusion in the Greek society. In order to achieve this, the dissertation attempts: a) to investigate qualitatively and quantitatively the impact of the programs and actions of NGOs in the field of combating poverty and social exclusion for the period 2000-2020 b) to investigate the impact of state’ s social policy on Greek society for the period 2000-2020 c) to investigate and propose possible and applicable directions for the social policy of a modern welfare state.