The two presidents held a private meeting at the Polish capital's Belweder Palace, where they also toured an exhibition about the work of Polish diplomacy during World War II and in the interwar period, the Polish presidential office said on Thursday.
It released no further details of the talks.
The Polish president said on Twitter: "Thank you very much, President Alar Karis, for your visit and a very interesting conversation. Estonia can always count on Poland as an ally and a partner."
Estonia's Karis tweeted: "It was nice to meet my colleague Andrzej Duda today in Warsaw. Estonia and Poland are connected by much more than history, we are connected by the future - excellent cooperation, whether in the digital or military sphere. And for many years of working together!"
He added that he was fascinated to see the Warsaw exhibition, which features a recently recovered archive of documents collected by Poland's former ambassador to Turkey, Michał Sokolnicki.
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Source: IAR, prezydent.pl