The challenges of adapting to the effects of climate change, the aim of improving quality of life, and concerns over the protection and enhancement of biodiversity, have led to policy and regulatory imperatives to integrate the concept of a good quality green network in urban planning. However, neither an urban ’green network’, nor ’good quality’, have been clearly defined either in practice or research. In addition, existing approaches to assessing the quality of urban green spaces focus on individual sites and do not assess the quality of a green network as a whole. This research suggests a definition both for an urban ’green network’ and for ’good quality’ on the basis of a literature review, and of content analyses of practitioners’ views and planning documents. It defines an urban green network as the green spaces in an urban area which perform a range of environmental and social functions and which need not necessarily be physically connected. It further defines good quality in terms of a network’s proximity, biodiversity, linkage, cooling, flood risk and quantity. Together, these six elements are defined as the ’network quality principles’. This thesis further proposes a new approach to measuring network quality, contending that assessment of the quality of an urban green network requires different methods and measures than those applied to individual sites. Accordingly, this thesis develops an approach whereby practitioners can develop appropriate indicators to measure network quality. It also provides a framework whereby indicator results can be scored and graded. The grade achieved ’signposts’ a potential policy direction to improve or maintain the quality of a network. The purpose of the approach is therefore to suggest the direction that policy could take in support of network quality, thereby helping to translate the concept of a good quality green network into urban planning. This thesis applies the approach using a Geographic Information System (GIS) in four UK pilot areas.