The former Australian coach will replace Daniel Vettori, who decided not to renew his contract at the club after being in the job for four years.
Lehmann guided the Heat to the title back in 2012-13 during his first stint at the team.
Signed on a two-year contract, the 49-year-old’s first task will be to rectify the team’s failure to make the knockouts this year.
"It was a wonderful experience at the time to be involved with building the Brisbane Heat at the start of the BBL and we had plenty of fun," Lehmann said in a statement.
"I enjoyed watching the BBL and the Heat during [this] season and, as a coach, I am pretty excited to be working with the Heat players, who I know are as talented and determined as anyone going around."
It’s great to be back @HeatBBL as coach. Thanks for the opportunity to move forward with a good young group of players and all the support we always get from the fans around Australia. 👍. Looking forward to seeing great crowds and fan support next year. #bringtheheat #BBL09 https://t.co/xbWvlaBP2h
— Darren Lehmann (@darren_lehmann) March 7, 2019
Lehmann stepped down as Australia coach post the ball-tampering scandal during the tour of South Africa in 2018, which led to lengthy bans for Steve Smith, David Warner and Cameron Bancroft.
"You learn a lot in dark times," he told reporters.
"For me, it's about enjoying the game. It's a great game we play, we're just custodians. For me, it's about getting the next generation through... It's about moving forward and loving the game."