This chapter analyses the impact of public administration regimes (PARs) and coproduction on hybrid organisations. The study of both PARs and co-production is a relatively new academic phenomenon, so there is still little systematic knowledge on how they impact on hybridity, and in particular how they impact on third sector organisations (TSOs). Yet, TSOs often work closely with public sector organisations, sometimes in partnership, so important changes in the way the public sector works have clear implications for TSOs and other hybrid organisations. For example, a major shift in the function and operation of traditional public administration occurred in the early 1980s that had clear and far-reaching ramifications for both the private and the third sectors. The growth and spread of a market ideology in the management of public services that later became known as New Public Management (NPM) brought with it a new focus and mode of operating, particularly in relation to the private and third sector providers of public services. So, it is impossible to ignore such sweeping changes in the public sector when considering hybridity and the third sector. Therefore, the purpose of this chapter is to clarify the impact of public administration regimes and co-production on hybridity, in particular in the third sector. This will be achieved in part by comparing and contrasting the values and goals of four PARs, with a focus on the role played by service users and professionals in the provision of publicly financed social services. The development of new PARs, such as New Public Management, contributes significantly to the complexity and hybridity facing the leaders of third sector providers of publicly financed services. The concept of co-production furthers the study with its focus on the mix of activities that both public agents and citizens contribute to the provision of public services. It also adds to the complexity and hybridity facing the leaders of third sector providers of publicly financed services. How these two concepts interact with each other and with hybridity are also explored in the following pages.