The 33-year-old forward has penned a one-year extension deal that will see him remain at the Shay until the end of the 2019 season.
Halifax-born Grix began his career with his hometown club in 2003, making 29 appearances before moving to Warrington Wolves.
He spent a decade with the Super League side before moving back to Halifax ahead of the 2016 season.
Grix has been a part of the Halifax side that reached the Qualifiers in 2017 and 2018 and the former Super League star says signing a new deal was an easy choice.
“I’m really happy to have signed a new deal,” Grix said.
“I’ve really enjoyed this past season, it’s been good.
“To be honest, I have thought about retiring a couple of times over the past couple of years, but we’ve got a really good group here who are really tight.
“I’ve really enjoyed this year and when it came to talking about staying for 2019, it didn’t take too much time to get that sorted.”
Head coach Richard Marshall feels that his side have "struggled" without Grix in the past.
And the Halifax boss admits he is grateful to be keeping the veteran forward for another season.
He said: "First and foremost, you notice when Simon doesn’t play,” said Marshall.
“We’ve struggled when he’s not been in the team.
“He’s a natural leader, he’s very aggressive and his ball handling skills are tremendous.
“He’s a really good leader of the group and a really good support for me as coach. He’s smart, academic, a solid pro and we’re lucky to have Simon to be honest.”