The expulsion of diplomats from the country where they are in charge is one of the problems that occur in relations between countries. One of the cases of expulsion of the diplomat is the case of the expulsion of 23 Russian diplomats from the United Kingdom that occurred in 2018. This expulsion is a continuation of the investigation of the attempted murder case against Sergei Skripal and his daughter, Yulia Skripal using a nerve agent. This study aims to find out the motives the United Kingdom expelled 23 Russian diplomats. The method used is a qualitative method with data collection techniques in the form of library research. The data used is secondary data. This research uses the theory of foreign policy and the concept of international diplomatic law. The decision to expel Russian diplomats was a British foreign policy carried out to protect the people and their country from all kinds of espionage activities carried out by Russia.