Scholars argue that Canada and other nations' best hopes for security against nuclear terrorism are to cooperate in order to prevent attacks. Looking into global conventions as collaboration between states allows us to observe state-level actions concerning terrorism, often seen as a non-state phenomenon. Assessing to what extent the international regimes address the states’ security concerns is crucial. The regimes that this thesis analyzes are the International Convention for the Suppression of Acts of Nuclear Terrorism (ICSANT) and the Nuclear Threat Initiative (NTI). The former is a major formal treaty that addresses nuclear terrorism concerns, and the latter is an informal international agreement dealing with nuclear threats. The central question of this thesis is: "to what extent does the NTI succeed in addressing gaps within the ICSANT?" Regime theory explores the emergence of cooperation between international organizations and is used to understand two different versions of collaboration, formal and informal, and through examining their emergence, advantages, limits, and the differences among actors involved. Through the analysis of both regimes and assessments from states and the United Nations specifically concerning ICSANT, this research provides a better understanding of the capacity of the international community to address complex and evolving security threats. This thesis demonstrates how the NTI addresses the gaps in the ICSANT to a medium extent, as the informality of the former helps fill nuclear related problems within the international community, while both regimes still share similar weaknesses. The NTI reaches a broader number and types of actors than the convention, supports the sharing of best practices and capacity building, develops and publicizes expertise, and influences global actors. However, it fails to reach reluctant states and to mandate measures comparable to the ICSANT.