Coach Alistair Edwards was dramatically sacked on Tuesday following a bitter feud with club captain Jacob Burns.
Many Glory fans have grown disillusioned after Edwards became the fifth coaching casualty since the A-League's inception in 2005.
But Perth have been boosted by the news that Sidnei has pledged his future to the club.
"It's a great sign of support for the club, and great news for the fans, that Sidnei has agreed to a further two years at Glory," said Glory CEO Jason Brewer.
"Sidnei has fast become a fan favourite and we all believe he has the potential to be one of the greats in the A-League.
"It's fantastic to see the reaction from fans when he gets the ball with his full arsenal of tricks and direct style of play."
The 27-year-old has set the competition on fire, netting twice and playing a hand in seven of Perth's 10 goals this season since arriving from Cypriot outfit Alki Larnaca.
"I'm enjoying it here at Perth Glory," he said. "It's a good professional organisation and that's important.
"I'm happy because it's a good club and I have a good relationship with the people here."