Melbourne confirmed it would not stand in the way of Moloney's move on Friday morning, leaving Moloney to sign a two-year deal with the Lions.
"We identified Brent as the type of player who we felt could assist our young midfield group," said Rob Kerr, the Lions national talent manager.
"He is strong at clearances - he ranked second in the AFL in 2011 - and that's an area we were certainly keen to bolster."
Moloney will join some of his new teammates on the Lions' high altitude training camp in Arizona.
Moloney underwent a routine medical examination with the Lions on Thursday while touring the club's facilities.
He won Melbourne's best and fairest in 2011 but struggled in 2012, playing 15 games with limited impact.
"Brisbane's a proud club with a good culture and I'm really looking forward to the opportunity," Moloney said on Thursday ahead of the medical testing at his new club.
"I just thought it was the right fit for me. They won 10 games last year, just outside the finals, and I'm looking to play finals footy and I think they've got a good young list."
