The aim of the article is to analyse and evaluate Poland’s attitude towards Ukraine’s aspirations to NATO membership. The main research problem is the question whether the authorities of sovereign Poland unambiguously supported the idea of Ukraine’s membership in NATO and whether they took measurable actions to implement it. The Polish authorities, regardless of political provenance, have invariably been in favour of NATO’s ‘open door’ policy since the end of the Cold War. They have supported the idea of including the post-Soviet republics, including Ukraine, in the Alliance. Ukraine’s entry into NATO is in Poland’s strategic interest, as it would almost cease to play the role of the Alliance’s flank state, which would significantly increase its security. The Polish authorities failed to convince NATO allies, mainly Western European countries, to include Ukraine in NATO, which was due to Russia’s strong opposition. However, new circumstances appeared with the Russian aggression against Ukraine in 2022. During the research, the method of content analysis of text sources was used.