The Post-Soviet regionalism is a new phenomenon and it requires a theory which addresses the very beginning of regional integration. Both Neofunctionalism and (liberal) intergovernmentalism conceptualize the very outset of European integration, thus, presenting the most adequate theoretical framework for understanding post-Soviet case of regionalism. This study seeks to contribute to a better understanding of the impediments to regional integration but also to conditions under which integration might succeed in Post-Soviet Eurasia. The numerous and unsuccessful attempts at regional integration in the post-Soviet Eurasia provide an opportunity to analyze the factors unfavorable to integration and to identify the impediments to this process. The issue motivating this study is that unsuccessful attempts should be analyzed not less than successful ones. Eurasian case is different from European integration due to different historical legacies, institutional choices, structural-developmental contexts and on-going state- and regime-building problems. Regionalism and democratic development are a salient feature of recent developments in Russia and the other republics of the former Soviet Union. The working premise is that through various regional arrangements that operate across Eurasia, countries will be able to find new cooperative solutions to existing problems. The main question is, given the undeniable advantages of the integration, why there has been little progress achieved? How the theories of regional integration can contribute to our understanding of the puzzles of Eurasian regionalism? To address this question, the paper focuses on a few theories of regional integration which will be applied to empirical analysis of post-Soviet Eurasia. The main focus is made on neofunctionalism. However, the study, will also consider the alternative explanation provided by (liberal) intergovernmentalism. The article also analyses the role of historical legacies and the attempts of post-Soviet states (PSSs) at regional integration and provides theoretical explanations of the outcome of these attempts. The analysis evaluates the outcome of post-Soviet Eurasian regionalism and tests the main theoretical assumptions. The analysis offered in this article aspires to contribute to the studies of comparative regionalism and area studies.