Walker has made three appearances this season, after joining the Centurions from Hull KR during 2014.
“Jonny is a great lad and very much a part of our ‘famileigh.’ As I have said previously it’s important that we find the right level of competitive fixture for all our players,” said Leigh’s head of rugby Derek Beaumont.
“You cannot win championships with a bare squad and must have strength in depth and unfortunately it makes it hard for players to break in from our reserves.
“Jonny is a Super League player and it is a mark of our squad that we have players of his standard out of the team.
“Whitehaven are a good club and Barry Richardson treats players very well. Jonny will be a significant addition to what (head coach) James Coyle is trying to achieve and Jonny is relishing the challenge to get some consistent game time to regain that sharpness that puts him at the top of his game.
“He is a no-nonsense runner with a big hit and I am sure the ‘Haven fans will take to his no-nonsense approach and embrace him like our fans have.
“We have an option to extend Jonny next year and it is important he has the game time at the right level to enable him to earn that.
“He is very positive and clear on what we want him to go and do and he is relishing the challenge which starts with Featherstone.”