In the two-day weekend referendum, a total 52.3 percent of voters backed the new constitution, drafted in a rare show of unity on Serbia's fractious political scene.
"This is the moment in which Serbia clearly approves its unity, that Kosovo is an integral part of Serbia," conservative Prime Minister Vojislav Kostunica said after the vote.
But analysts said the new charter would have almost no impact on UN-backed negotiations over the province's future status.
This is despite having a preamble that says "all state institutions” should “defend Serbian interests in Kosovo".
Since February, Belgrade and the leaders of Kosovo's ethnic Albanian majority have been engaged in talks on the future of the southern Serbian province, which is expected to gain a form of independence by the year's end.
"The mere fact that Kosovo was included in the new constitution will have no influence on the course of the negotiations" over its status, said analyst Milica Delevic-Djilas.
Analyst Djordje Vukadinovic estimated that the new charter would "not strengthen Belgrade's position much" over Kosovo.
Since they started in February, the talks have only succeeded in frustrating the diplomats involved, bearing no results with the two sides deeply entrenched in their opposing positions.
Kosovo Albanian leaders are seeking nothing short of independence in the talks, while Belgrade says it is only prepared to offer them broad autonomy.
Ethnic Albanians, who outnumber Serbs and other minorities in Kosovo by around nine-to-one, ignored the referendum as if it was being held in another country.
But Kosovo's Serb minority of about 100,000 voted in force in the hope that the province, which they see as the cradle of their nation, can remain within Serbia.
In a bid to strengthen Serbia's stance, Prime Minister Kostunica warned that those supporting Kosovo's independence would suffer "consequences".
"Such a step will have a direct impact on the relations between Serbia and any countries that recognise Kosovo," local media quoted Mr Kostunica as saying in an interview with Russian television.
Mr Kostunica's chief adviser, Vladeta Jankovic, said one of the "most precious results" of the new charter was that a majority of the voters confirmed the constitution preamble on the territorial integrity of Serbia.
"A key point of Belgrade's stance in the negotiations will remain the same: to respect and follow rules and regulations of the international law," Jankovic said.
Legal expert Slobodan Vucetic estimated that the charter vote could send an important message to the international community.
"The international community can conclude that the majority of citizens support the stance that Serbia is a united state whose territory cannot be cut off and whose borders cannot be changed," said Mr Vucetic.
The turnout at the referendum was low despite a strong campaign by all major parties and the Serbian Orthodox Church urging voters to back the new charter, which officials vowed would help keep Kosovo within Serbia's borders.
"Political parties have obviously failed to recognise the main motives within the electorate," said Zoran Lucic of the Centre for Free Elections and Democracy, the referendum's official monitor.
"The times have changed. [Slobodan] Milosevic could use Kosovo as a wildcard to have a massive turnout at the elections, but this is not the case now," he explained, referring to the late Serbian strongman.
The failure to gain popular support for the constitution would have been a major blow to Mr Kostunica's coalition government.
The European Union suspended integration talks with Belgrade in May because of its failure to arrest a top war crimes fugitives such as former Bosnian Serb general Ratko Mladic.
Delevic-Djilas warned the new charter could be a positive step for Serbia only if it leads to a solution of political issues such as the arrest of Mr Mladic and other war crimes fugitives and resolving Kosovo's status.
“If we continue living in Groundhog Day', then the constitution alone won't bring any great changes," she said, referring to a US movie in which history continually repeats itself.