Serbia has started formal accession talks with the EU with the goal of joining the 28-nation bloc.
Serbian PM Ivica Dacic said the EU "is not only the goal, but also the means by which we will modernise our system".
The membership negotiations are expected to take several years, as Serbia has to bring its laws and institutions into line with EU norms.
Greek Foreign Minister Evangelos Venizelos led the EU team in Brussels. Greece is now chairing EU meetings.
The BBC's Guy De Launey in Belgrade says the Serbian government is led by former ultra-nationalists who converted to the cause of EU membership before they came to power two years ago.
Aleksandar Vucic, leader of the largest party in the governing coalition, has been the driving force, our correspondent says.
He told the BBC that joining the EU was the only sure way to transform Serbia after two decades of conflict, international embargoes and economic woe.
"If we don't change ourselves, if we don't do something regarding rule of law, if we don't do many other changes in other social spheres - we won't be successful in the future," he said.
Serbia's membership negotiations are expected to take at least six years.
Serbia's agreement to normalise relations with Kosovo was the key which allowed membership talks to start. Kosovo broke away from Serbia in a conflict in 1999 and declared independence in 2008 - a move that was condemned by Belgrade.
But a Kosovo-Serbia deal was struck through EU mediation last year.
The EU Ambassador to Serbia, Michael Davenport, told the BBC that "Serbia has made a lot of progress over the last three or four years - putting much stronger emphasis on regional co-operation, and in particular trying to sort out the issue of Kosovo".