International relations theory has traditionally placed alliance politics at the very center of many analyses of international or regional politics. But international relations theory (I.R.) has also been characterized by struggles between competing paradigms and schools of thought, or what is sometimes referred to as “theoretical sectarianism”. Scholars of Middle East regional politics, in contrast, have rarely associated with a single school or perspective, and have been more likely to employ a kind of theoretical pluralism to understand the details and nuances of regional political life, including alliances. This kind of scholarly eclecticism is even more important today, in the post-Arab Spring era, as the region has been characterized by rising regional instability even as a traditional hegemonic power – the United States – has declined in relative power and influence over regional affairs. The many regional and global changes, in short, have not led to the apparent triumph of any particular theoretical approach, but rather have underscored the salience of multiple I.R. theory perspectives in understanding the politics of shifting regional alliances. This essay examines key findings in the alliance theory literature, examining realist, liberal, constructivist, political economy, and regime security approaches to regional alliance dynamics. It then turns to major alliance shifts during and after the 2011 Arab uprisings, comparing the theoretical expectations to the empirical record of shifting regional alliances. Based on the empirical analysis, I argue that regional alliances in actual practice have drawn on the entire range of expected behaviors – balancing, bandwagoning, omnibalancing, underbalancing, budget security, and more; but that all these machinations also underscore the premium put on regime security by each of these states, including their reads of ideational, economic, and domestic political dissent as primary security threats, even stronger than external or more direct military ones. If anything, the relative decline of U.S. power seems to have led states to be even more obsessive about their own regime security and the role of regional alliances in ensuring regime survival. Understanding these changing regional alliance dynamics therefore suggests the importance of the theoretical pluralism mentioned above, but it should also lead us to expect more fluidity and volatility in alliance patterns in the post-American era in the region.