The 36-year-old former England all-rounder is due to jet out to Australia in December to join the Heat as he continues his remarkable return to cricket.
Having retiring in September 2010 on the advice of medical experts, Flintoff has put his injury problems behind him and was back playing Twenty20 for his beloved Lancashire last season, helping the county reach the final.
And with Flintoff now a specialised Twenty20 player, the charismatic Englishman will link up with former Lancashire team-mates Daniel Vettori and Law, who insists the veteran remains as committed as ever.
"I've told Fred we signed him to win games of cricket, so that means we want him bowling 140km/hr, hitting sixes and using his experience around the group to get the job done," Law told the Heat's official website.
"He's an enormous competitor and so I know he is coming out for the right reasons.
"The Brisbane fans will quickly discover he’s a champion fella and I'm sure they will love having him with the team.
"He's a wonderful person and we're looking forward to having Fred and his family with us at the Heat over the summer."
Flintoff, was on the verge of signing for the Heat in 2009 before injury scuppered the move, said: "I'm excited to be coming back to Australia and especially to Brisbane, which has always been a favourite spot of mine to play.
"Stuart and I have had a few conversations and I'm clear on what we're looking to achieve in the competition.
"The Heat squad has some exciting talent and I'm looking forward to catching up with Dan Vettori again.
"I really enjoyed my T20 season with Lancs and having the opportunity to keep playing is something I am very pleased about."
The Big Bash season – which will also feature Flintoff's former England team-mate Kevin Pietersen at the Melbourne Stars – gets underway on December 18 with the final scheduled to be played on January 28.