There was no letting up from Leeds as they put the game to bed with a 69th-minute third through Jack Harrison, before Chelsea’s close-season signing Kalidou Koulibaly was sent off late on.
A second victory from three at the start of the new campaign came at a canter from there on in, helping Leeds climb up to second in the standings with seven points, while Chelsea’s first loss leaves them down in 12th with four.
“We scored an own goal and conceded from a set piece,” Chelsea coach Thomas Tuchel said. “The defeat is nothing to do with pressing, nothing to do with running less kilometres and nothing to do with the style of Leeds.
“We were able to be the better team. But then it was 2-0 and our body language was not like it was in the last match. I don’t see the connection that we lost to the style of Leeds. We knew it was coming.”
Looking to get back to winning ways after a fiery draw with Tottenham Hotspur last time out, Chelsea flew out of the traps, with close season signing Raheem Sterling flashing a strike wide after just 36 seconds.
Tackles were flying in in the West Yorkshire sunshine as the intensity levels remained high. Harrison also went close early on, while Sterling had the ball in the net 15 minutes in, but was correctly ruled offside.
Mason Mount was next to go close, bringing a fine save out of home goalkeeper Illan Meslier, only for Mendy to gift the hosts the lead.
The Senegal international made a mess of collecting a back pass from Thiago Silva, he was then dispossessed by Aaronson, who was free to walk the ball home.
The home fans enjoyed the opener against traditionally one of their fiercest rivals -- animosity that stretches back to the 1970s -- with the roof almost coming off Elland Road after in-form Brazilian forward Rodrigo headed home the second from Harrison’s free kick.
Tuchel rang the changes in the second half, but the visitors, other than Reece James’ drilled effort that was tipped wide by Meslier, never looked like getting into the match.
Harrison’s close-range finish was no more than the home side deserved, ensuring they could stroll to a second successive home league win -- a feat they did not achieve all last season.
A second yellow card for an innocuous foul from Koulibaly left the home fans heading for the exits with a beaming smile.
“It was the best performance since I have been here,” Marsch said. “You are starting to see a bunch of players who understand their role, some in the form of their lives.
“Our way of playing dictated the match. We made them make mistakes. These quality players can pass the ball all day if we give them time. We wanted to make them uncomfortable, and today we did.”