This thesis looks at the regional approach to the regulation of foreign investment in Southern and Eastern Africa through the Regional Economic Communities of COMESA and SADC to determine whether this approach is a viable means of regulating investment in these regions given the issues raised in the investor-State arbitrations faced by their Member States. The thesis highlights areas of convergence between the national and regional investment instruments and between the bilateral and regional investment instruments. An examination of the implementation of regional economic community laws and the emerging jurisprudence from the regional judicial bodies highlights the existing gaps between the requirements set out in the regional investment instruments, on the one hand, and the realities and capabilities of implementing them under the current institutions, on the other. Based on this, the thesis examines the validity of pursuing a regional approach of regulating foreign investment in COMESA and SADC.