Having featured for Norwegian first-division champions Viking FK for the past three seasons, the Roar announced on Saturday the star forward had completed a loan to the A-League Men side.
It comes after D'Agostino struggled to make an impact for Viking in 2025, playing just 10 games and scoring two goals after undergoing ankle surgery early in the season.
Although the forward did start for the Socceroos in the 2-1 loss to the US in October, competition for the striker's position is sure to be intense for the World Cup, to be held in the US, Canada and Mexico from June 11 to July 19.
With many Socceroos featuring in European competitions, including Mo Toure, Zac Sapsford, Apostolos Stamatelopoulos, Martin Boyle and Noah Botic, D'Agostino will need to push his case for the tournament.
A move to Brisbane, who have struggled to find the net this season, could help both the side and the 27-year-old.
D'Agostino hasn't played since early November after an injury ruled him out of the final weeks of the Norwegian season.
He played under current Socceroos coach Tony Popovic with Perth Glory in 2019-20 and for two seasons with Melbourne Victory, netting 16 goals across the three campaigns.
D'Agostino returns to the Roar, having made more than 30 appearances for the club between 2015 and 2018, before joining the Glory and Victory.
"It's fantastic to be back home and putting on the Brisbane Roar jersey once again," he said.
"The Roar was where my football journey really took shape, and I'm hungry to fight for the badge and help push the team forward and win matches."
D'Agostino moved to Viking FK in 2023 and made about 50 appearances for the side.
Roar chief operations officer Zac Anderson says bringing the star striker back to Brisbane is significant for the club.
"As a current Socceroo, his decision to return speaks volumes about the direction we are heading," Anderson said.
"Nick brings intensity, professionalism and a genuine hunger to succeed, and we're excited to see him lead from the front and represent our supporters."