Via Sistina was given a perfect ride by James McDonald, the champion jockey making it four straight wins in the $5m feature.
Treasurethe Moment ran a gallant race for third, looking the winner turning for home.
McDonald has now won four Cox Plates.
“I think this one is relief,” the jockey said post-race.
“I love this place, I’m blessed to ride champion racehorses, blessed to be a part of a champion stable. She was trained to the minute. I can’t thank Waller team (enough) – they’re just exceptional horse people.
“Even though it wasn’t seven lengths, I’m just over the moon.
This year’s edition of the famous weight-for-age race holds special significance. It’s the last running of the race before Moonee Valley undergoes a massive $220 million refiguration.
The Cox Plate will take place at Flemington in 2026 before returning to a new-look Moonee Valley in 2027.