Jancevski scored in the fourth minute before debutant, injury replacement player Holly Furphy, added another in the 77th minute.
Victory (27 points) claimed their second win on the bounce to at least temporarily overtake Melbourne City (26 points) in the race for the premiership plate.
But the loss leaves the two-time defending champion Sky Blues still eight points outside the top six. Â
Victory needed less than four minutes to take the lead.
Jancevski, an attacker pinch-hitting at left-back, stood over a free kick about 25 yards out from goal on the right hand side.
The left footer struck the ball sweetly and it kept rising into the top corner for her fourth goal of the season.
But Jancevski suffered a ball to the head in the 18th minute and was checked on again after the half-hour mark before being substituted at half-time.
Oh my word, WHAT A HIT �🤯 One of the best free kicks you'll see this season! — Ninja A-League (@aleaguewomen) 🗣� "That is unsaveable" - childhood @gomvfc fan Alana Jancevski produces something ������� four minutes into the Big Blue! Just wait until you see the reverse angle 🫢Watch #MVCvSYD live… pic.twitter.com/K5cvXlPsNpJanuary 24, 2025
Sydney's Caley Tallon-Henniker nudged a shot past the post in the 40th minute and forced a save from Courtney Newbon minutes later.
Sydney were lively after the break, with Margaux Chauvet lifting a shot over the bar in the 64th minute.
But Sydney couldn't make a chance stick and Victory made them pay.
Rachel Lowe slipped through Furphy and the youngster rounded Brianna Edwards to score a lovely goal on a tight angle.
Furphy had only been officially announced as an injury replacement signing for Paige Zois on Friday.
Sydney defender Faye Bryson tried her luck from distance in the 87th minute but Newbon was able to claim it.
Victory will take confidence from the win into next Saturday's derby against CityÂ
Things don't grow any easier for Sydney, who face Adelaide on Friday.