According to the first exit polls, Milanović was barely above 50 percent of the votes, which would have meant that a second round of voting would not be necessary.
But late on Sunday evening, the election commission announced that a second round of voting will be held in two weeks.
Milanović received 49 percent of the votes in the first round, while challenger Dragan Primorac received 19 percent of the votes, according to the election commission.
Zoran Milanović has previously been the leader of the Social Democrats, while Dragan Primorac belongs to the conservative HDZ, which holds the government power in Croatia.
However, the incumbent president Milanović has made a political journey where he is now sharply critical of both the EU and NATO, and he has criticized the sanctions against Russia, which are directed against the country due to the invasion war in Ukraine.
The President of Croatia has some power in the country's foreign and security policy. He is also the commander-in-chief of Croatia's armed forces.
