The article comprehensively analyses the phenomenon of Portugal's neutrality during the Second World War. The analysis is made by the single case study method, using historical, as well as economic and statistical instruments. The research objective of the article is to point out the key features of Portugal's neutrality during the Second World War by identifying its causes, features and key aspects. The first part of the article contains the analysis of the causes of the Portuguese neutrality: economic and military weakness, the «syndrome» of negative experience of participation in a world war after the First World War, as well as the unwillingness to enter into war neither against the Allies, in particular, the United Kingdom, with which Portugal had a centuries-old alliance and profound economic ties, neither against the Axis, whose countries were ideologically close to Portugal. The author also explores the policy of «swinging» between the Allies and the Axis countries, military and politically, as well as economically. In military and political terms, Portugal did remain neutral until the breakthrough of 1943, after which Portugal sided with the Allies, giving the United States and the United Kingdom an access to military bases. In the economic sense, Portugal strictly adhered to the «classical neutrality». Besides, the article analyzes the policy of Portugal in achieving «Iberian neutrality», that is, to ensure Spain not entering the war. The author concludes that Portuguese neutrality can be called «classical» both economically and, with reservations, politically. Portuguese neutrality is a unique case of the non-involvement of a colonial power in the world war and an example of a successful and flexible balancing between two opposing blocs.