Sent to the front by Shinn when Jeff Lloyd slowed the pace on early leader Honorius, Junoob was never threatened, defeating Criterion by one and three-quarter lengths with the winner's stablemate Bagman one and a quarter length back in third.
Trainer Chris Waller said the heavy tracks in Sydney of late made it hard to access Junoob's form.
As I've said the last few weeks it's been hard to know where we're at but you can't panic and we've stuck to our plan," Waller said following the race.
"Today we were going to know whether he's come up or not and he needed those two runs of the heavy track to be fit enough for today.
"It helps to have a smart rider aboard who took the race by the neck at the 1600 metre mark and lead."
It was the third win on the day for Shinn who rode Junoob to victory in the Group III Neville Sellwood Stakes in April.
"He's a big free-striding horse and he can be a little bit lethargic from the gates," Shinn said.
"There was a lack of tempo prior to the race and I just didn't want to be on the back foot and out the back with no chance.
"I just wanted to make sure that he stepped on the right foot and I got him into a prominent position.
"He was never going to lose, he got into a great rhythm and quickened at the 600.
"He had some form lines behind Streama last weekend and when he got a soft run he was always going to be hard to run down."
A 7yo gelding, Junoob takes his overall record to 5 wins, 3 seconds and 2 thirds from 16 starts for earnings of $575,112.
The Shadwell homebred is a son of Haafhd the Champion 3yr old in Europe in 2004 with victories in the 2,000 Guineas and Champion Stakes.
Haafhd now stands at Beechwood Grange Stud in England at a fee of £3000.
Junoob's dam, Faydah (Bahri), is a half-sister to Group 1 Queen Elizabeth II Stakes and Group II Queen Anne Stakes winner and sire Lahib.