Flynn, who has tested superbly at this week's NAB AFL Draft Combine, flew to Adelaide on Sunday and trained at the club's Alberton Oval base on Monday.
He met coach Ken Hinkley, assistant Alan Richardson, fitness boss Darren Burgess and a few Power players, and immediately knew it felt right.
"We've had some interest in him for quite some time obviously and then when he was coming out for the draft camp we probably got on the front foot quite quickly," Hinkley said on Thursday.
"We knew there was some stuff we really liked, and we've got Alan Richardson who has worked with some of the Irish boys in the past and had some great success.
"We thought what a great opportunity for a club."
The 20-year-old has been signed on a two-year deal following some excellent testing at the combine.
On Wednesday he ran 2.83 seconds over the 20-metre sprint, 24.25 in the repeat sprint, and 8.08 in the agility test.
His foot skills and athleticism was again on show on Thursday, as the players were tested for their kicking, handballing and goalkicking.
After playing a game for the European Legion against the AIS-AFL Academy in London earlier this year, Flynn said he had pushed to join an AFL list.
"It's very similar to back home and I like the physicality side of it as well," Flynn said.
"I know [Port Adelaide] has made great strides in the last 18 months and they're putting a lot of work in and they're on the up."
Twitter: @AFL_CalTwomey
