The possibility of the UK's withdrawal from the European Union has never been more realistic and up-to-date since joining the European Communities (EC) as it is today. The UK is facing a unique situation. At present, this depends solely on the capabilities of European and British government officials, who negotiate the terms of withdrawal and future cooperation between the two entities. The main goal of this paper is based on the British – Slovak trade relations development analysis to figure out their impact within the Brexit consequences on the future Slovak economy and its current status in international economic relations. The paper also provides a basic overview of Brexit process and its possible impact on the EU's further functioning. Basic data will be drawn from generally accepted institutions, evaluating the UK and Slovak trade and economic performance. To accomplish this goal, methods such as analysis and comparison to illustrate the UK-Slovak foreign trade development, synthesis and logical deduction to discuss the Brexit impact on Slovak economic environment in the future are to be used; data from scientific and professional publications, periodical and non-periodical press. The paper presents the results of an empirical analysis, which showed that because of the size of economic relations between Slovakia and the United Kingdom and the number of goods and services being exported to the UK, the «hard» Brexit will be very unfavourable for Slovak foreign trade due to the possible tariffs being imposed. The research empirically confirms and theoretically proves that it can cause a significant weakening and slowdown in the Slovak economy. Either way, the upcoming Brexit process, that is the withdrawal of Great Britain from the European Union, would have a major impact not only on British, European but also on the world economy. The impact of Brexit on Slovakia's economy will not only be in reducing the possible growth of the economy, but also in employment and price increases. Keywords: EU single market, Britain's withdrawal from the EU, foreign trade policy instruments analysis, international economics, Slovak economy slowdown prediction, Slovak foreign trade commodity structure analysis.