Until midday on Wednesday the Lions were negotiating with both South Australian clubs after the 21-year-old requested a trade to his home state.
However, it is understood Polec made the decision to nominate the Power on Wednesday, with negotiations entering their 12th day.
Recruited with pick No.5 in the 2010 NAB AFL Draft, Polec has played 16 games in three seasons.
His management company, Elite Sports Properties, had suggested the midfielder would nominate a club if a deal had not taken shape by the middle of this week.
"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 on Wednesday afternoon.
With Adelaide still keen to recruit Polec, the Lions will continue to search for the best deal they can.
"Jared expressed a desire to go home, but he is not a free agent so we will continue speaking with both Port Adelaide and Adelaide," national talent manager Rob Kerr told lions.com.au.
Crows list manager David Noble said: "We understand Jared has nominated a club to try to speed up the process, but the reality is no trade has been done yet. We'll continue to talk to Jared's management and Brisbane, and keep an eye on the situation."
