Tadic travelled back to the Serbian bank of the Danube river aboard the Golubica (Dove) ferry.
He was seen off in the Vukovar river port by Croatian President Ivo Josipovic, Vukovar-Srijem County Prefect Bozo Galic and Vukovar Mayor Zeljko Sabo.
Earlier in the day, after a wreath-laying ceremony at the Ovcara memorial site in memory of 200 Croatian prisoners of war and civilians who were taken from the Vukovar hospital and killed at Ovcara in November 1991 by Serb paramilitaries and the then Yugoslav People's Army (JNA), Tadic expressed regret at innocent victims and apologised for crimes.
"Admitting crimes and expressing apology and regret create possibilities for forgiveness and reconciliation," Tadic told reporters at Ovcara.
Croatian Prime Minister Jadranka Kosor joined the two presidents during their talks in Srijem Palace.
In Paulin Dvor, a village outside Osijek, Presidents Tadic and Josipovic laid wreaths in tribute to 18 Serb civilians and one Hungarian killed by Croatian forces in December 1991.