Ridden by Damien Oliver and having just his fifth race, the son of Declaration of War (USA) charged home over the final furlong to nab Junipal on the line, scoring a narrow win.
"This horse can really stay," said Oliver.
"He didn't quite get into the Derby, but he was so strong to the line today."
Vow and Declare (image Grant Courtney) broke his maiden at his previous run when winning over 2381 metres at Warrnambool.
"He's a very promising young horse and hopefully we'll be back for the bigger races next year. He's an elite stayer in the making."
Passed in at the Inglis Classic Yearling Sale when offered by Kitchwin Hills and retained to race by his breeder, Vow and Declare has now won two of five starts earning over $100,000 in prizemoney.
He is a half-brother to tough stakes-winning stayer Lycurgus from good producing Testa Rossa mare Geblitz, who comes from the family of Group I winners Hauraki and Kidnapped.
Geblitz has no yearling, but produced a filly this spring by Star Witness that is a full sister to Lycurgus.
Vow and Declare is the first Australian stakes-winner for War Front's Group I winning son Declaration of War, who shuttled to Coolmore for two seasons and is standing the 2019 Northern Hemisphere season in Japan.
He is the ninth stakes-winner worldwide for Declaration of War, who sired Olmedo to win this year's Group I Longchamp Poule d'Essai des Poulains.