Bertrand Traore, a 17-year-old Burkina Faso international and trialist, scored after six minutes and De Bruyne doubled the advantage after 29 minutes before going off with a knee injury which did not prevent him from joining his team-mates on the bench for the final quarter of the match.
Romelu Lukaku added a third in first-half stoppage time and Victor Moses added an 89th-minute fourth.
The biggest roar of the night came when Nizad Ayub headed a stoppage-time consolation as Jose Mourinho recorded a second win of his second spell as boss at Stamford Bridge.
Mark Schwarzer made his first Chelsea appearance in goal and Traore also started in a team which mixed experience and youth.
Carlo Ancelotti's first match in charge of Real Madrid saw them stroll to a stylish 6-0 win over Bournemouth at Dean Court.
Cristiano Ronaldo netted the first goal of the Italian's reign and added another before Sami Khedira scored on the stroke of half-time.
Bournemouth, whose chairman Eddie Mitchell said this fixture was a reward for their long-suffering support, failed to provide a goal for them to cheer as Gonzalo Higuain, Angel Di Maria and then Casemiro got in on the act.
Ancelotti, Jose Mourinho's replacement, included new signing Isco in his line-up and there was certainly enough household names in his first Madrid XI to keep the capacity crowd, many of whom had paid £60 and queued overnight for their ticket, happy.
Swansea registered their sixth win of pre-season after they saw off Exeter 2-0 at St James' Park.
Nathan Dyer gave them the lead after 10 minutes with an accomplished finish and Rory Donnelly made sure of the win in the second half, converting Jonjo Shelvey's pass.
The Swans continue their preparations for next season with a trip to Reading next weekend.
Norwich lost 1-0 to San Jose Earthquakes in their pre-season friendly at the Buck Shaw Stadium.
New signings Ricky van Wolfswinkel and Leroy Fer played 45 minutes each, but could not prevent Cordell Cato's seventh-minute goal deciding the match.
Canaries boss Chris Hughton refused to be down beat, saying on the club website: "I thought Ricky looked really sharp and Leroy was prepared to get on the ball and show some of the qualities of his game, but there were a lot of pluses."
MK Dons preserved their unbeaten run in pre-season with a 1-1 draw against a youthful Plymouth.
The League Two side went ahead through Ryan Lane in the second half with a spectacular 30-yard effort.
But Karl Robinson's men hit back three minutes before full-time when Daniel Powell struck a deflected effort home.
Argyle's next outing is against Yeovil next Saturday.
St Johnstone followed up their Europa League success in Norway with a pre-season draw against Dundee.
The Perth men made the short journey east to Dens Park for the summer warm-up clash just three days after stunning Rosenborg in their second qualifying round first-leg tie with Frazer Wright's first-half winner.
There were further positive signs when striker Stevie May put the McDiarmid men ahead early in the first half, but Dundee claimed a stalemate with former Celtic youth Carlo Monti's second-half leveller.
European hero Wright was given the day off for the meeting with John Brown's team, although Tam Scobbie, Dave Mackay, Paddy Cregg and David Wotherspoon were all in the starting line-up after seeing duty in Trondheim.
Former Rangers, Dunfermline and Aberdeen midfielder Barry Nicholson, meanwhile, was one of two trialists named on the Saints bench by boss Tommy Wright.
The visitors struck early as May put them ahead. The forward latched on to Liam Caddis' through ball and was clinical with his low finish past Kyle Letheran in the Dee goal.
Substitute Monti restored parity after the break but Saints saw a late chance to claim the win wasted when Letheran denied May a second from the penalty spot.