Winger Murphy, 29, joined from Wakefield Trinity in 2012 and has gone on to score 75 tries in 166 matches for the club.
Huddersfield coach Simon Woolford switched him to second-row last term and - given the way he adjusted - that now seems his most likely position for 2019.
Ferguson, meanwhile, is in his second spell with the club having re-joined from Bradford Bulls two years ago.
The 30-year-old was named Scotland’s new captain earlier this week and is seen as another key asset in Giants’ bid to push for the top-five.
“These deals were done a while back and I’m happy to endorse them, have the guys around for another two years and be part of the 2019 squad which I expect will still evolve and develop as time moves on,” said Woolford.
“On Murph, he’s simply tough as old boots, a great pro and one of those under-rated sort of guys who goes under the radar a bit but exactly the type of player you want in and around the joint.
“Players love playing alongside him and I’m expecting the move up to second-row to be a new lease of life for him.
“He’ll be fit and ready to go in November and he can bring a lot to the team as he can also do centre or wing if things need moving around in a game.”
Woolford, who helped transform Giants season after taking over in May, added: “Dale needs a full off-season training hard to get his body right and on the tapes I saw and what he’s done for us when I’ve had him he can be an asset to us in the back-row when fully firing.
“I reckon he’s like a number of players in that the World Cup didn’t do him any favours this year so we’re both looking forward to starting up again in November and seeing the real Fergy back out there come February time.”