Starting his career at Adelaide United, Toure returns to Australia from FC Tulsa in the USL Championship after stints in Turkey and France.
The Roar have added former Burnley No.9 Chris Long, the 30-year-old becoming the sixth signing under new coach Michael Valkanis.Â
Toure, 25, shapes as a crucial piece up front in Sydney's chances for finals this season after a raft of off-season exits.
Reigning Golden Boot winner Adrian Segecic, Polish striker Patryk Klimala, Socceroos midfielder Anthony Caceres and German attacking midfielder Anas Ouahim were among the departures.
The Sky Blues will be out for atonement after failing to make finals last season under coach Ufuk Talay, finishing seventh with a 10-7-9 record.
Toure made his way up the ranks at Adelaide United alongside brothers Musa and two-cap Socceroos striker Mohamed, who are at Danish Superliga club Randers FC.
He is a two-time Australia Cup winner, having scored in every round - apart from the semi-final - in Adelaide's winning run in 2019 to earn the Mark Viduka Medal.
Toure then added to his trophy cabinet after making the switch to Macarthur, scoring again in the 2022 final for the Bulls.
"We've had an eye on Al Hassan for a bit as he is a quick, strong player and he will be able to give us plenty of versatility in the front third as we can deploy him as a striker and a winger," Talay said.
"He is very talented in a one-on-one situation, and we believe he will help us break lines with his speed and the forward runs that he can provide us."
Part of Everton's academy, Long bounced between clubs before aiding Burnley's promotion to the Premier League.
He arrives in Brisbane after recent stints at Motherwell and Crewe Alexandra.
Valkanis, the Roar's fourth full-time coach in less than three years, expects the seasoned professional to add composure and dash up front for the three-time A-League champions, who narrowly avoided last year's wooden spoon.
"I know I'm joining a club that has big ambitions for the upcoming season," Long said of his first posting outside of England and Scotland.
"Can't wait to get going, meet my teammates and, most importantly, pull on that jersey and give my all for the fans."