Djukanovic was backed by 180,272 voters out of 340,462 who went to the polls on April 15, the country's election commission said in a statement on Sunday.
Mladen Bojanic from the Positive Montenegro party came in second with 33.4 %, or 111,711 votes.
Draginja Vuksanovic, MP of the Social Democratic Party and the first female presidential candidate in the history of Montenegro, secured 8.20% of the vote, while Marko Milacic, founder and current president of extra-parliamentary populist political party True Montenegro, trailed behind with 2.81%.
Hazbija Kalac, the leader of the Party for Justice and Peace, won 0.80% of the vote, businessman and independent Vasilije Milickovic had 0.48%, and Dobrilo Dedeic, a representative of the Serbian coalition, had 0.41%.
Djukanovic is leader of political party DPS, which has been in power since the introduction of multi-party system in 1990. He served as prime minister of Montenegro from 1991 to 1998, as president of the country from 1998 to 2002, and as prime minister again from 2003 to 2006, from 2008 to 2010, and from 2012 to 2016.
The incumbent president of Montenegro, Filip Vujanovic, was reelected in the first round of the 2013 election on 51.2% of the vote. Vujanovic is ineligible in the April elections as under the Montenegrin Constitution a president can serve up to two terms in office.