The 56-year-old is the frontrunner, and a recent survey indicated that he may even achieve the feat already in the first round by winning more than half of the ballots cast.
Djukanovic already served as head of state once and was prime minister six times since first taking the post, in 1991, except during three withdrawals when he said he wanted to take care of his private business.
He always kept the strings of power in his hands as the chief of the Democratic Party of Socialists (DPS), which has reigned without interruption for 27 years.
Djukanovic said that his return aims to stabilize Montenegro's pro-Western path amid regional and global instability and "defend" it from Moscow's influence.
The DPS accused Moscow of involvement in an alleged coup attempt in October 2016 and has joined all Western sanctions against Moscow.
His main rival, Mladen Bojanic, was put forward by the leading opposition party, the Democratic Front, which favours closer ties with Russia and accuses Djukanovic of nepotism and corruption.
None of the remaining five candidates is expected to achieve percentages in the double digits.