Vucic won 58.55 per cent of the vote, the State Election Commission said on Monday after counting 96.19 per cent of ballots, though his Serbian Progressive Party (SNS) fell short of a majority - 42.92 per cent - in concurrent voting for parliament.
Opposition presidential candidate Zdravko Ponos, a retired army general, garnered 18.34 per cent, while his United for Victory alliance obtained 13.6 per cent. The Socialist Party of Serbia, a longtime SNS ally, came third with 11.51 per cent.
The preliminary outcome suggested the SNS would have to seek coalition partners to solidify its domination in the 250-seat parliament, after a 2020 vote that was largely boycotted by the opposition, which left the SNS and its allies with 188 seats.
Under Serbia's constitution, a new government must be formed within 90 days of parliament being sworn in.
Vucic, a former nationalist firebrand accused by the opposition of autocratic tendencies and corruption - allegations he denies - ran for a second five-year term on a pledge of peace and stability following Russia's invasion of Ukraine on February 24.
The invasion has prompted the most severe international sanctions ever against a major power, putting Serbia under Western pressure to choose between its historically warm relations with Moscow and aspirations to join the EU.
In his victory speech, Vucic said Serbia plans to maintain "friendly and partnership relations" with Russia. He said Serbia would stick to its balancing act between its EU membership bid and close ties with Russia and China, a major investor.
He spoke as Western powers including France, Germany, Britain and the United States prepared to tighten sanctions against Moscow after Ukraine accused Russian forces of atrocities against civilians in the Kyiv region.
The Kremlin categorically denied any accusations related to the murder of civilians in the town of Bucha.
Russian President Vladimir Putin congratulated Vucic on his victory. "I expect that your activity...will continue to contribute to the strengthening of the strategic partnership... between our countries," Putin said in a telegram to Vucic.
Sasa Djogovic, an analyst with the Belgrade-based Institute for Market Research, said Serbia would have to swing away from Russia if it wanted closer links with the EU, and even join some sanctions against Moscow.
"I believe that the president of Serbia...is quite realistic...and that we will strive to have this (new) government as least pro-Russian as possible," he said.
Serbia is almost entirely dependent on Russian gas for its energy and its army maintains ties with Russia's military. The Kremlin has also supported Serbian opposition to the independence of Kosovo by blocking UN membership for Belgrade's former southern province.
Although Serbia backed two United Nations resolutions condemning Russia's invasion of Ukraine, it refused to join in sanctions against Moscow.
