The highly-rated midfielder will be with the Giants until at least the end of the 2029 season after resisting overtures to return to his Victorian home for a four-year contract extension.
Off-contract at the end of this season, the 21-year-old reportedly turned down a monster $17 million, 10-year deal from St Kilda to remain in NSW.
"I didn't find (re-signing) difficult. It was pretty straightforward," Callaghan said on Monday, adding he had told his manager "I really want to stay at the Giants".
"It was a pretty smooth process and it didn't take too long to get it all sorted.
"I always wanted to stay at the club."
The four-year Giants deal will take Callaghan to free agency.
"I haven't thought about the length of the contract too much," Callaghan said.
"Four years to free agency was what me and my manager discussed as the best option.
"There's so many games and stuff in between that, so I just want to keep improving and keep developing as a player and person.
"I'll take care of that when the time comes."
Callaghan has been instrumental for the Giants in the engine room alongside Tom Green, averaging 23 disposals, 3.6 tackles, and 3.4 clearances per game last year - his third season at AFL level.
He shapes as a vital cog in the Giants' push for their maiden premiership.
"We're right in the premiership window and that's something I really want to be a part of," Callaghan said.
"I wouldn't want to leave now.
"We can definitely win over the next few years and to be a first premiership player for the Giants is something that would be amazing."
He is the latest in a long line of GWS stars - including Jesse Hogan, Brent Daniels, Aaron Cadman and Sam Taylor - to sign contract extensions.
Left burning after a straight-set finals exit, GWS will kick off their 2025 season by hosting Collingwood at Engie Stadium on March 9.
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