Mata kicked off the the initiative, a non-governmental organisation that supports football charities around the world, last August and has since been followed by a host of players including Bayern Munich's Mats Hummels, Juventus defender Giorgio Chiellini and USA World Cup winners Megan Rapinoe and Alex Morgan.
Brosque is now the eighth player worldwide to join the initiative but the first Australian and first from the Asian region.
The 34-year-old Sky Blue striker will now donate at least 1% of his salary to charity Football United, aimed at empowering young people in diverse Asian communities, and Mata could not be happier with his decision.
"For more than a decade, Alex has led by example both on and off the pitch," Mata said.
"He's an excellent addition to the team and we couldn't have hoped for a better player to bring Common Goal down under for the first time."
The two-time A-League champion feels being a figure in such a global sport is an opportunity to give back.
"I've always felt that, as footballers, we have quite a unique capacity to drive positive change," Brosque told Sydney FC.
"Football is far and away the most popular sport on the planet and collectively our actions have the potential to set an example for many others to follow.
"What drew me to Common Goal was the idea of uniting different players from all over the world behind a shared commitment to give back.
"It's not hard to see how this could really take off and inspire a new culture of giving not only from footballers but also the broader football community."