The "Student List – Students Win" took 52.9 percent of the vote, which would give it 140 seats in the 250-seat parliament, according to final projections by CeSID, an election-monitoring group, and the Ipsos agency.
Vučić’s "United Serbia" list, with the former president as its candidate for prime minister, won 38.8 percent and 103 seats.
Crowds poured onto the streets of Belgrade to celebrate after Vučić conceded defeat.
The movement grew out of almost two years of protests after the collapse of a canopy at Novi Sad railway station, which killed 16 people.
It has promised to fight corruption, protect the independence of courts and prosecutors, make public spending more transparent, reform education and healthcare, support young families and lower the cost of living.
European Council President Antonio Costa and European Commission President Ursula von der Leyen congratulated the winners, saying the EU was ready to support reforms on the rule of law, media freedom and the fight against corruption.
EU enlargement commissioner Marta Kos said a new chapter could open for Serbia, while Hungary’s Prime Minister Péter Magyar and Montenegrin leaders also sent congratulations.
However, the result does not mean a sharp break in every area.
The group do not support recognising Kosovo’s independence and oppose sanctions on Russia, positions close to those of the outgoing authorities.
The movement is also divided on closer integration with the EU.
(ał)
Source: PAP, IAR