Both have roots in the Chiefs region: Dewes, a former Fiji Test player and forwards coach, played for Counties Manukau and Thames Valley while Gibbes had a distinguished career for Waikato, the Chiefs and the Māori All Blacks.
Dewes, who played 28 Tests for Fiji, said he was honoured to join the Chiefs as scrum coach.
"This is an incredible opportunity to work alongside world-class players, coaching staff and management. I'm excited for the challenges ahead and eager to build on the strong foundation already set in place."
Dewes' coaching experience includes specialist roles with the Blues A and Under-20s side and the Northland Taniwha since 2020.
Gibbes, an eight-Test All Black and 68-game veteran for the Chiefs from 2001-08, is the New Zealand Under-20s coach. He has coaching experience with Leinster, where he was forwards coach from 2008-14, Clermont Auvergne (2014-17), Ulster (2017-18), Waikato (2018), and director of rugby for La Rochelle (2018-21) before another stint with Clermont Auvergne (2021-23).
He was a resource coach for the Chiefs organisation in 2024.
Gibbes said, "I'm thrilled to be more involved with the Chiefs this season and have the privilege of being part of coaching the team I once played for.
"We have a superb group of hardworking men who are great to work with, so it's an exciting opportunity to help them succeed."
Chiefs chief executive Simon Graafhuis said they were glad to have the pair as part of the team.
"Graham has jumped the ranks a bit by going from NPC to international coaching, but having the experience he's gained with us for the coming season will be a real asset.
"Jono has already contributed a lot to the club since rejoining us at the end of last year, and we are grateful he has extended his role for the 2025 season. He is well respected by the players and staff, and we look forward to seeing the team's development with his additional involvement."
This week, the pair stepped into their roles, taking over from departing assistants, scrum coach Nick White and lineout and forwards coach Ross Filipo.