The article analyzes the process of confirmation of the Polish-German border in the course of German reunification. The Federal Republic of Germany previously contested the ultimate nature of this border under international law. This caused serious political conflicts in relations between the People’s Republic of Poland and the Federal Republic of Germany. This was not changed by the Treaty on the Normalization of Relations between the two States, signed on December 7, 1970. The rise of a democratic Poland in 1989 and the parallel reunification of Germany put an end to these conflicts. This was reflected in the Treaty on the Confirmation of the Polish-German border (signed on November 14, 1990) and in the “two plus four” Treaty (signed on September 12, 1990). This became the basis for building the Polish-German “community of interests” in a united Europe, as postulated by Minister Krzysztof Skubiszewski. It should be remembered that the negotiations on the border Confirmation Treaty contributed to the development of the concept of a Treaty on good neighborhood and friendly cooperation. It was signed on June 17, 1991. It set the directions for the Polish- -German “community of interests” and paved the way for Poland to enter the European Union.