The methodological framework presented in this guidance document outlines the integrated assessment approach being implemented in support of the Regional Initiative for the Assessment of the Impact of Climate Change on Water Resources and Socio-Economic Vulnerability in the Arab Region. The approach combines climate change impact assessment and vulnerability assessment tools into a five step integrated assessment methodology that is based on global climate modelling, regional climate modelling, hydrological modelling, vulnerability analysis and integrated mapping tools. The guidance document aims to facilitate understanding of the methodological framework that will generate findings for informing and fostering policy dialogue on the expected impacts and implications of climate change on sustainable development in the Arab region.