The Man City playmaker assisted Thorgan Hazard's 55th-minute equaliser and then clinched the 2-1 win with an outstanding finish 20 minutes from time.
Five days after midfielder Christian Eriksen had suffered a cardiac arrest on the same Parken Stadium pitch, Yussuf Poulsen fired the Danes into an early lead as FIFA's number one-ranked team were outplayed until De Bruyne arrived to light up proceedings.
Kasper Hjulmand's men could hardly have got off to a better start when they took the lead with less than two minutes gone.
Jason Denayer's careless pass out of defence was picked off by Pierre-Emile Hojbjerg and when he fed Poulsen, the striker smashed a low shot across keeper Thibaut Courtois and inside the far post.
Play stopped briefly as the clocked ticked around to 10 - the shirt number worn by Eriksen - as the players of both sides and officials joined the spectators in a moving moment's applause for the Inter Milan midfielder.
Roberto Martinez sent on De Bruyne as a half-time substitute in a desperate search for inspiration - he was soon to be followed by Axel Witsel and Eden Hazard - and the move paid dividends within 10 minutes.
Romelu Lukaku ran away from the Danish defence before squaring for De Bruyne, who expertly dummied his way into space before rolling the ball into the path of the fast-arriving Thorgan Hazard to thump into the net.
But it was his sumptuous 70th-minute strike, which flew past the helpless Schmeichel and into the bottom corner, which ultimately won the day and maintained the Red Devils' perfect start.
Martin Braithwaite might have rescued a point three minutes from time, but saw his header from substitute Andreas Skov Olsen's cross clip the crossbar and run away to safety.
Belgium's final group game will come against Finland this Monday night.
With a place in the Last 16 already secured, the Red Devils can afford to relax and rest tired bodies.
On the other hand, they could field another strong side and continue to build momentum ahead of the knockout stages.
Denmark, meanwhile, face a must-win game with Russia. Qualification to the next stage of the tournament is still possible for the Danes but anything other than a victory will see them eliminated.