The 30-year-old former Widnes player joined the Centurions on a 12-month contract from Toronto Wolfpack last November and is keen to stay despite the threat of relegation from Super League.
“It’s been a crazy year in so many ways with the pandemic and the way the season has gone,” he said. “But I still feel the same way about Leigh as the day I first signed.
“It’s a great club with fantastic facilities and the potential here is immense. Leigh is a real rugby town and the fans are very passionate.
“If we can put together a team that can compete week in, week out and string some wins together, we have a potentially-massive fan base. It’s all about unlocking that potential and I want to play my part in doing that.
“If the whole squad plays well together, we have the potential to end this season with some wins that will change people’s opinions of us.
“We just need something to kick-start us to turn things around and we are determined to do that.”
Leigh interim coach Kurt Haggerty said: “It’s important we as a club retain our best players and Joe is certainly one of those.
“He is a competitor and wants to progress his career with Leigh Centurions, which is most important.”
Mellor’s retention follows the signing of forwards Sam Stone and Jai Whitbread from NRL club Gold Coast Titans.
Second-rower Stone, 23, and prop Whtibread, also 23, will join the Centurons with immediate effect from Gold Coast Titans.
Haggerty said: “We are very pleased to have Sam on board. He is a player who we have monitored closely and it’s great to finally get the deal over the line.
“Getting Jai is a major coup for us. He’s a front-rower who can play at loose forward. He is good with the ball and also very tough defensively. I’m sure he will fit in really well and I’m looking forward to having him on board.”