"It's a little bit sad to move away," the key defender told Trade Radio.
"I've been there since I was 21 and they were the team that gave me an opportunity.
"The Adelaide Footy Club are rebuilding a little bit now so I saw it as an opportunity to extend my career."
A father to one-year-old daughter Hazel, Hartigan said the opportunity to return to his native state was a chance that was too difficult to ignore.
"It was more the family factor.
"No one has been able to visit us this year (during COVID).
"To come home and have family around was a massive factor, and the opportunity to come to Hawthorn and play in defence."
With James Frawley retiring and James Sicily to miss most of the 2021 season with a knee injury, Hartigan and Sam Frost will represent the Hawks key defensive make-up.
The 28-year-old expressed his excitement about the opportunity of taking on the bigger bodies of opposition forwards and said he is confident of playing well into his 30s.
"I'm not putting any gauges on it being two years - I'd love to play for as long as I can.
"I still feel there's an opportunity to play some really good footy over the next four to five years."
We task the new kids with asking each other the hard hitting questions.
03:37
The Pace on this Kid is INSANE | Cody Anderson 2024 Draft Highlights
Hawthorn has selected Next Generation Academy product Cody Anderson with Pick 64 in the 2024 Telstra AFL Draft. A strong inside midfielder and pressure forward, Anderson has seen his draft stocks rise following his solid form for the Eastern Ranges in the Coates Talent League this year.
02:30
Noah Mraz is OURS | 2024 Draft Highlights
Noah Mraz is our newest Hawk!
01:48
Rugby turned AFL Rookie dons the Brown and Gold
Here from newly signed Category B Rookie, Matt Hill as he talks about his first day at Waverley.