Ahern, 20, has had his right knee reconstructed twice this year.
His most recent operation was in September, and North Melbourne football manager Cameron Joyce told AFL.com.au the Victorian was likely to miss the entire 2017 season.
“He’s still got some rehabilitation with his knee to get over next year but we’re taking a longer-term view with Paul,” Joyce said.
“We’ve had doctors check that out thoroughly and we’re certainly happy to take that on … and we can look at a start in 2018.”
Ahern is a classy midfielder who can make an impact up forward. He had been contracted at the Giants until the end of 2017.
AFL.com.au reported last week the Giants were looking to offload Ahern, Will Hoskin-Elliott and Jarrod Pickett to free up salary cap space.
“[Ahern] adds some real flexibility to our team in terms of his lateral movement and his kick. He can play multiple roles through the midfield and forward,” Joyce said.
Ahern was drafted at No. 7 in 2014.
Giants football manager Wayne Campbell told the GWS website the club wanted to allow Ahern a fresh start.
“Paul has had a frustrating start to his career due to injury but his determination and resilience has been admired by all at the Giants,” Campbell said.
“We thank Paul for his contribution to the Giants over the past two years and wish him well for the rest of his career.”