Summary: The article attempts a brief assessment of changes in the Polish Armed Forces resulting from Poland’s membership in NATO. A chronological narrative presents the conditions related to changes in the security environment of Poland, the transformation of NATO and the evolution of the security and defence policy of the Republic of Poland, which influenced the development and technical modernization of the Polish Armed Forces in the past quarter of a century. The analysis and assessment have been related to the period preceding Poland’s accession to NATO, the frst and the beginning of the second decades of membership, and then the changes caused by Russian aggression in 2014 and the Russian war against Ukraine started in 2022.