With both sides having recently struggled domestically, it was not really a surprise to see so few shots on goal in the first half.
However, Monaco only needed one on target to take the lead after the half-hour mark, with Takumi Minamino squaring for his opposite winger Mathys Detourbet, who tapped home his first goal for the club since joining on loan from Manchester City this summer.
Nordsjaelland offered little in response, in truth, with their only attempt falling to centre-back Victor Nelsson, who got his header all wrong from a corner.
The second half was much livelier, and Monaco thought they doubled their advantage early on when Paris Brunner turned and found the bottom corner for what would have been his ninth goal of the campaign, but it was ruled out for offside.
It did not take long for the hosts to find the net again with the same two players combining from the first goal - but after Minamino had diverted Detourbet’s cross home, again it was disallowed for offside.
Monaco were scratching their heads, wondering how they were not further in front, and that feeling deepened when Folarin Balogun - fresh after opening his account for the season in defeat to Paris FC - headed straight at Andreas Hansen just a few yards from goal.
Despite only being a goal down in the latter stages, Nordsjaelland still failed to work Lukas Hradecky, and if anything Monaco looked more likely to extend their lead, with Minamino’s volley stinging the palms of Hansen.
However, the goalkeeper could not stop Matthis Abline, as Detourbet sent him through one-on-one in stoppage time, allowing Monaco’s substitute to find the bottom corner.
As a result, the French side open a major European campaign with a third straight win for the first time in 30 years. Ultimately, Nordsjaelland just could not find a way past a Monaco side unbeaten on home soil this season (W5, D2), as the Danes remain winless in the league phase (D2, L1).