Mr Djukanovic told jubilant supporters gathered in the government building in the capital Podgorica that his coalition For European Montenegro had won an absolute majority of parliament seats in Sunday's polls.
"I can say with certainty that we have 42 and that we are fighting for the 43rd mandate" in the 81-seat Montenegrin parliament, the prime minister said.
Initial projections given by non-governmental observers from the Centre for Monitoring (CEMI) showed that the coalition was on the threshold of gaining a majority of seats in the parliament.
Another observer group, Center for Democratic Transition (CDT) said
Mr Djukanovic's coalition has "probably won 41 mandates" that would enable it to form a government alone.
Preliminary official results were expected later today.
Djukanovic celebrates
Opening a bottle of champagne to celebrate the victory, Mr Djukanovic told his supporters that the vote "is a triumph for pro-European policy in Montenegro."
"Montenegro is firm in its European path and has the authorities that, with such a strong support by its citizens, can make crucial steps towards European integration," Mr Djukanovic said.
Voter turnout in the tiny Balkan state of just 650,000 people reached nearly 70 percent, with the election generating little of the passion and excitement that saw 85 percent of registered voters cast ballots in the independence referendum in May.
Mr Djukanovic's ruling coalition had been widely expected to win the polls, riding a wave of goodwill that followed the proclamation of independence from Serbia on June 3 and Montenegro's prompt acceptance as the newest member of the United Nations.
The longest-serving politician in all six former communist Yugoslav republics, Mr Djukanovic was the key architect of Montenegro's independence drive.
He has campaigned hard on the issue of fast-track integration into the EU, pushing for an association and stabilization agreement to be signed by the end of this year as a first step towards joining the 25-member bloc.
The main opposition bloc led by the pro-Serbian Socialist People's Party of Predrag Bulatovic was expected to win 11 seats, the same as the new political force, the Movement for Change, a non-governmental organisation-turned-party, estimates showed.
Many voters seemed unwilling to embrace the prospect of a change of government at such a crucial juncture, especially given divisions within the opposition, who had been unable to focus their attention on much-needed social, economic or political reforms.
Alongside the general election, voters were also choosing representatives for their local assemblies and mayors in 14 towns and municipalities throughout the country.