The winner came in the 30th minute after Remy collected Eden Hazard’s cross outside the box and skipped his way past a couple of defenders before shooting past Vedran Janjetovic.
Although the hosts had a handful of shots on target, they couldn’t trouble Petr Cech in the Blues goal.
And when they did find the back of the net two minutes from time, Sebastian Ryall was deemed to have handled the ball.
Once again Cech started in goal, in what could be his last appearance for the Blues amid specualtion of a move away from the club. Joining him in the line-up were youngsters Nathan Ake at left-back and Jeremie Boga in central midfield.
The hosts started the game with a narrow formation as they looked to stop Hazard, but Diego Costa nearly scored seven minutes in. The striker jinked his way into the box and it looked like his shot was going to sneak under Janjetovic, before the goalkeeper recovered to grab the ball before it crossed the line.
Just a couple of minutes later, the hosts had their first chance as Robert Stambolziev’s shot deflected off John Terry, but Cech was there to collect.
Chelsea took the lead when Hazard played Remy in on the edge of the box and the striker bypassed the Sydney defence and turned to send a left-foot shot into the top corner.
The Premier League champions began to take control as Namanja Matic shot straight at the goalkeeper and Remy sent an effort wide before Stambolziev had another chance for the hosts, but he blazed it over the bar.
Chelsea continued to attack through Costa in particular, but their top scorer was out of luck as he saw his chance saved, moments before being replaced by Ruben Loftus-Cheek in the 40th minute.
Remy nearly had his second 10 minutes after the break, but he couldn’t get his shot down and saw it sail past the post.
It was all Chelsea until the last 10 minutes when Sydney looked more threatening. George Blackwood had three chances to level the game but when Cech couldn’t get the ball, Branislav Ivanovic was there to head it off the line.
Then two minutes from the end of normal time, the hosts got the ball in the back of the net. Aaron Calver’s header was blocked by Cech and Ryall managed to send the ball over the line but it was ruled out for handball.