Juan Mata continued his amazing recent form with his third goal in three games but it took a superb free-kick from David Luiz to open the floodgates as Mata and Ramires sent the European champions top of Group E.
Before that, there were as many questions as answers at the Parken Stadium in Copenhagen as Chelsea almost let another lead slip two weeks after blowing a two-goal advantage to draw their opening match against Juventus.
Roberto Di Matteo had described this game as Chelsea's biggest of the group and they certainly started as if they meant business, Jores Okore hitting his own post clearing Oscar's cross, with Victor Moses poised to nod home.
Chelsea punished a Nordsjaelland mistake ruthlessly in the 33rd minute, Fernando Torres robbing Enoch Adu and finding Frank Lampard, who showed great vision in feeding Mata to slot home.
Nordsjaelland then assumed total control as Mikkel Beckmann sent a looping header just over from Okore's long ball, Petr Cech only parried Nicolai Stokholm's swerving 25-yarder and Mikkel Beckmann screwed Michael Parkhurst's cross wide.
Chelsea withdrew Moses for Eden Hazard and Nordsjaelland sent on Mario Ticinovic for Morten Nordstrand and it was the home side's change which almost paid off when Cech brilliantly saved Joshua John's curler onto the post and Ashley Cole was on hand to block Beckmann's rebound.
But 11 minutes from time, Luiz swerved a vicious free-kick in off the inside of the near post.
It was game over three minutes later when the champions' best move of the match ended with a lucky break off a defender, with Mata stroking home.
And there was still time for Ramires to put gloss on the scoreline by tapping home Oscar's cross.
Source: PA
Source: PA