"Russia has always respected the bravery and heroism of the Polish people, soldiers and officers, who stood up first against Nazism in 1939," Putin said during a meeting with Polish Prime Minister Donald Tusk in the Baltic Sea resort town of Sopot.
Tusk said Putin's visit reflected a growing spirit of cooperation despite remaining differences.
"We are making another step toward strengthening confidence in the past so that we can build our future on it," Tusk said.
U.S. President Barack Obama did not attend the memorial ceremonies, attended by some 20 European leaders, but was represented by his national security adviser, retired Gen. Jim Jones.
Many Poles saw Obama's absence as a snub, The New York Times said.
Putin offered to open Russia's national archives on the Katyn massacre, where Russian soldiers in 1940 killed 21,768 Polish officers and intellectuals being held as prisoners of war, EUobserver reported.
He also signed an agreement giving Polish ships passage through a Russian-controlled gap in a Baltic Sea promontory to Poland's freshwater Vistula Lagoon, near Gdansk Bay.