The Lyon striker earned an international recall in November and, on his sixth appearance for France, netted the opener before Olivier Giroud joined him on the scoresheet at the Stade Geoffroy-Guichard.
Lacazette got France off to an ideal start when he seized on a loose ball to fire past Kasper Schmeichel 14 minutes in as he opened his France account on his second start for his country.
Giroud's first international goal since the World Cup win over Switzerland doubled the lead before half-time, with a cross from Michael Krohn-Dehli hitting the post prior to half-time for the visitors.
It was a brief respite in a first half dominated by the hosts, although Denmark did keep goalkeeper Stephane Ruffier busy after the interval.
The Saint-Etienne man coped with what Lars Jacobsen and Nicklas Bendtner had to throw at him, on his home ground, as Didier Deschamps' men saw out a relatively comfortable victory.
Having seen his first-choice side beaten convincingly 3-1 by Brazil on Thursday, Deschamps handed chances to some of his fringe players.
And the France coach saw his much-changed XI make a bright start in Saint-Etienne as Lacazette broke the deadlock.
Antoine Griezmann - who retained his starting spot from the Brazil defeat - had his chipped effort saved by Schmeichel before Lacazette fired in the rebound.
At the other end, Ruffier was quiet early on only his third France start, with Lacazette almost doubling his tally before the half-hour, only for Schmeichel to save his prodded effort.
The barrage continued, Dimitri Payet the next to go close as France's attacking quartet of Lacazette, Griezmann, Payet and Olivier Giroud caused no end of problems.
Denmark looked to have steadied themselves before the break, but France doubled their advantage when Giroud slipped Geoffrey Kondogbia's throughball underneath Schmeichel.
Krohn-Dehli's teasing delivery struck the post prior to the interval and it offered a sign of things to come in the second half, as Morten Olsen's men began to control proceedings.
Despite enjoying greater possession, Denmark struggled to ask questions of Laurent Koscielny and Raphael Varane at the back, although Ruffier was troubled when he could only parry Jacobsen's long-range drive precariously over.
Ruffier then flung himself to save Bendtner's strike as Denmark showed glimpses of why they appear on course to return to France for next year's European showpiece.
The only sour point for Deschamps was the injury that forced full-back Christophe Jallet off late in the game.
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