Davies has signed a four-year deal, while Callard, who was out of contract, has committed himself to Leeds for the next two years.
Davies – who won 46 caps for Wales between 1985 and 1995 – joined Leeds in 1996 and has guided them into England's top flight from the depths of National Division Three.
Highly-rated as a coach, Davies' name has already been bandied about as a potential successor to current Wales coach Steve Hansen who is set to return to his native New Zealand at the end of RWC 2003. But after signing a new contract, Davies has committed himself to Leeds for the foreseeable future.
"Our achievements last year were a tremendous credit to the team and the players' efforts," said Davies.
"In our recruitment policy this summer we have tried to bring in young, exciting players who will give us longevity. I want to continue and build on the success we have already gained."
Meanwhile, Callard, who won five caps as England fullback in the 1990s, arrived at the club at the start of the 2002/03 season after parting company from Bath and has also earned rave reviews for his coaching ability, even turning down an offer from Irish province Leinster during the off-season.
Chief Executive Gary Hetherington said: "We have recognised the tremendous impact our entire coaching team have had on our success and we are delighted that Phil and Jon have agreed to their new deals.
"We have also signed new contracts with Steve Carter and Simon Middleton to complete our coaching team."
