Leckie's commitment for 2026-27, with a trigger for another season beyond that, comes as Western Sydney delight in former Johnny Warren Medallist Nicolas Milanovic's return.
City star Leckie, 35, fought through a horror run of soft-tissue injuries plus hip surgery to crack Tony Popovic's squad for this year's World Cup.
The attacker, one of just four Socceroos to have played at four World Cups, started Australia's second game against the US, but suffered a hamstring injury that ultimately ended his tournament.
City have backed Melburnian Leckie, who when fit is one of their most important players in midfield, to return to his best.
"Mat has consistently shown that when he's on the pitch, he remains one of the A-League's most influential players," football director Michael Petrillo said.
"... We're confident Mat has plenty more to contribute and we're delighted he'll continue in City blue for the season ahead."
Leckie added: "I've loved representing my hometown club over the past five years, and I'm really pleased to be staying for another season."
On Friday night, Western Sydney confirmed the long-expected return of Milanovic.
The 24-year-old exploded in the 2024-25 season, scoring 12 goals and starring for the Wanderers, with his attacking midfield form notably among the reasons Juan Mata couldn't get a start there.
Milanovic earned his high-profile move to Aberdeen then his first Socceroos call-up and caps against New Zealand in October 2025.
But he struggled in Scotland and returns after just a year away to re-join Western Sydney on a three-year deal.
"Coming back to the Wanderers just felt right," Milanovic said.
"The opportunity to play overseas challenged me in a lot of ways and helped me grow as a player, and as a person.
"I'll bring those experiences back with me, but I'm excited to be home and focus on what's ahead."
New Wanderers coach Ufuk Talay added: "His experience overseas will help him, but for me it's about making sure he enjoys his football again.
"When Nic is playing with confidence and freedom, he's one of the best players in the competition."
Milanovic only made 10 starts for the Dons and 23 appearances in all, registering one assist.
"Returning to a club and league where he previously enjoyed so much success gives him a great opportunity to get his career back on track," Aberdeen manager Stephen Robinson said.
"From our perspective, we've secured a good fee and retained future economic rights to the player, so it's a deal that makes sense for everyone involved."
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