The Middle East is a place that has been destined to be in the middle of the earth, a region where its name came from the European perspective. The region has been loosely defined to include definitive and limited countries; different sources have different countries that represent the Middle East. Historically, varied empires and colonies have dominated the Middle East, producing a region with micro-societies that have different cultures, religions, and languages. The result is a region where continuous conflicts and tensions take a place. On top of that, the lack of security in the Middle East came from the regional structural system, where there is dangerous multipolarity, and no overarching regional hegemon power, resulting in regional competition tearing the security fabric of the Middle East. This was exacerbated by the declining role of the United States in the region, leaving a vacuum of power, and pushing the regional states to compete for regional hegemony. Therefore, the Middle East has been plagued by proxy wars, terrorism, civil conflicts, and territorial disputes. The increasing tensions between Iran and Israel in the last decade, chiefly because of the Iranian nuclear program, have prompted this thesis to explore and investigate the security role of Iran and Israel in the Middle East. Iran, since the Islamic Revolution in 1979, the country adopted a new political and ideological system based on the Islamic Shi'a principles. The new Iran perused regional expansionism rhetoric, where it believed that the Middle Eastern governments should be purified from the western mentality and secularism and adopt an Islamic government similar to that of Iran. In addition, there have been security concerns about Iran's nuclear program, which was reflected by the regional perception of it. Israel, is a state that was established with the help of the United Kingdom in 1948. Israel believed that they belong to Palestine for historic and religious reasons, considering Jerusalem as a sacred land for them. Israel also has been the single state in the Middle East that has nuclear weapons, which disturbs the security balance of the region. In the light of the abovementioned argument, this thesis aims to investigate Iran and Israel's threat to the Middle East from different perspectives; (1) their ideological affinities; (2) Weapons of Mass Destruction (WMDs) ambitions; and (3) the regional security perceptions about them. The evaluation will take into consideration the ongoing regional changes, which include; the US's declining role in the Middle East, and the economic crises. The thesis employed a qualitative approach, with a Regional Security Complex theoretical framework, and relied on existing knowledge and structured interviews. The results showed that Iran's ideology harms the stability of the Middle East, however, in terms of WMDs Israel poses a larger threat than Iran's nuclear program, yet, the recent political and economic developments have pushed the regional states towards Israel.