Polec, who was taken by the Lions with at No.5 in the 2011 national draft, walked out on the club at the end of the 2013 season saying he wanted to return to his home state of South Australia.
Port Adelaide and Adelaide were both keen on Polec, but the 21-year-old has chosen Ken Hinkley's much-improved outfit.
"Port Adelaide is delighted with this announcement and will now work closely with the Brisbane Lions to work towards a suitable trade for both clubs," the Power said in a statement.
"Neither Port Adelaide, Jared nor his management team will make any further comment until confirmation of an official trade has been reached with the Brisbane Lions."
Polec is one of several promising Brisbane youngsters hoping to switch clubs during the off-season.
Billy Longer, Elliot Yeo, Sam Docherty and Patrick Karnezis have also been linked with other teams.