A late header from Western Sydney captain Mitch Duke brought a dramatic end to Sydney FC's 13-game undefeated A-League streak on Friday night.
An assist from Tate Russell in the 81st minute put the Socceroo square in front of goal to nail the header and give Wanderers an unlikely 1-0 victory.
In a thumping atmosphere at the sold out Netstrata Jubilee Stadium, the Wanderers handed the Sky Blues their first loss since round three.
The competition leaders must have thought they were seeing double -- that previous reverse was also a 1-0 defeat to their city neighbours.
A raucous crowd of more than 18,500 was kept on the edge of their seats throughout as both sides created chances but were denied by good defending.
The Sky Blues were kept in check by the Wanderers all across the park and signs of frustration started to show as time ran down.
Effective tactics from Wanderers' caretaker coach Jean-Paul de Marigny kept the ladder leaders searching for space they were not afforded.
The win is the second in a row for Western Sydney, who are now undefeated from four games under De Marigny since he took over from sacked coach Markus Babbel.
Wanderers fans at the southern end of the stadium intensified the atmosphere on the night by setting off at least five flares throughout the match, while the antics continued outside the ground, leaving the club open to sanctions from the FFA.
The fiery feelings were also apparent on the field, with Daniel Georgievski copping a late red card for lashing out with a boot at Marco Tillio's face after an untidy challenge.
In-form Wanderers midfielder Bruce Kamau was taken off in the 55th minute with what looked like an adductor injury.
Sydney FC will travel to play Melbourne Victory at Marvel Stadium on March 7, while the Wanderers face Brisbane Roar at Suncorp Stadium on March 6.