Abstract: Sub-Saharan African economies have been inextricably linked for centuries. Traders, often belonging to the same ethnic group or family, have been regularly crossing what are now borders to exchange goods and services, giving rise to intense flows that account for a significant part of the continent’s total trade. The formation of trade blocs and integration of economics in the world has increased in the recent past. Institutions and organizations have been developed in order to; facilitate trade and other economic matters, combine resources for the achievement of common goals, and strengthen international and intercultural dialogue. Kenya, Uganda and Tanzania are among the East African countries that have through the East African Community implemented most of these policies. On the other hand, the world is experiencing deglobalisation and a shift towards nationalization. With these parallel processes, the presence of sub-national governments through various forms of decentralization continues to influence the implementation of regional trading arrangements. This study examined the role of sub-national governments in safeguarding of cross border investments and trade within the East African Community member states of Kenya, Uganda and Tanzania. The objective scope of the study was to analyze the implementation of the East African Community Common Market Protocol by sub-national governments in Kenya, Uganda and Tanzania in relation to cross border investments and trade. The study was informed by theories on Regional Integration and International Trade. This study utilized a combination of the case research designs and library research. The study employed mainly primary data from interviews and secondary data that included published works/books, papers, journals, the internet and other unpublished works. Key Words: sub-national governments, cross-border investment, trade, regional integration