In the first ever Melbourne derby grand final, winger Yonatan Cohen handed City the lead in the 10th minute in front of a sellout, largely pro-Victory crowd at AAMI Park.
The crowd of 29,902 was a sporting record crowd at the venue.
Victory unsuccessfully appealed for a handball penalty off German Ferreyra in the 80th minute, but referee Adam Kersey wasn't swayed and they were unable to manufacture an equaliser.
Coach Aurelio Vidmar's surprise decision to play Leckie in defensive midfield paid off as the Socceroo turned in a commanding performance to win the Joe Marston Medal as player of the match.
In his first start since returning from injury Leckie had his nose split open by an accidental boot from Zinedine Machach in the 49th minute but played on admirably with a massive bandage around his face.
"My teammates are just so strong," skipper Aziz Behich told Network Ten.
"You see Leckie leading by example today, can't even see out of that strapping band, but what I am so proud of this team is everyone contributed this season."
This season, City overcame multiple horror runs with injury to just finish second behind Auckland FC, before earning a home grand final.
It was Vidmar's first championship and just his second win over Victory in 18 attempts as coach of either Adelaide or City.
City's defence were superb as they condemned Victory to a second consecutive grand final defeat and extended their championship drought to seven years.
Trewin and Germain Ferreyra completely shut down Bruno Fornaroli while full-backs Nathaniel Atkinson and Behich were aggressive, with Cohen a constant threat.
Victory's star winger Nishan Velupillay (ankle) failed to prove his fitness and was clearly missed while Victory's Daniel Arzani and Machach were lively without an end product.
Arthur Diles's charges started hot but City scored off their first touch in Victory's box.
Behich nutmegged Josh Rawlins with a wonderful backheel to find Andreas Kuen.
The Austrian cut back the ball for Max Caputo, whose shot hit the bar before Israeli winger Cohen drove home the rebound.
In the 20th minute, Leckie desperately blocked Machach's close-range shot.
Jack Duncan made a wonderful diving save off Leckie in the 23rd minute before Patrick Beach denied Machach up the other end.
A minute into the second half, Duncan made a terrific fingertip save to stop Cohen curling a second goal into the top corner.
Max Caputo and Cohen both spurned chances to make it 2-0 before the Victory handball call.
