This research examines the effects of Brexit in 2016 on the economic and political security of Northern Ireland. The primary objective of this study is to identify how a policy of a certain group of countries can have a significant impact on other countries such as Northern Ireland. To analyse this issue, the research employs the concept of national security, with a specific focus on economic and political security. A descriptive qualitative method is employed to collect data through a review of relevant literature. Authors find that Brexit brought about Northern Ireland's economic and political security which has led to a disrupted supply of goods, a rise in prices, a decline in people's welfare, and a clash between Unionists and Nationalists, resulting in the overthrow of the Northern Ireland Prime Minister.