The younger Cahill, 18, joins Ross Aloisi’s Roar team after spending four years in England.
Shae, a midfielder, spent last season playing in the English Premier League’s under-18 competition, recording three assists in nine games.
“We are pleased to announce the signing of Shae Cahill from Everton’s world class academy,” the Roar’s chief executive Kaz Patafta said.
“Securing such a promising young midfielder is a testament to our club’s new vision of integrating youthful talent into our squad and first team environment.
“Shae’s addition promises an exciting era ahead for the Roar family.”
Tim Cahill, the nation’s leading goal scorer, expressed pride over his son’s first senior deal.
“Very proud of you my man @shaeloucahill,” Cahill commented on the Roar’s announcement post on Instagram.
“Wishing you all the best @brisbaneroarfc keep chasing your dreams.”
Tim Cahill scored 50 goals in 108 appearances for Australia, he also netted 169 goals in 683 club games, most famously starring for Everton in the EPL.