Initially off-contract at the end of this year, Simonsson had faced an uncertain future as the Eels weigh up their roster options for 2025.
But he was offered a deal after meeting with Ryles, becoming the club's first re-signing since Ryles left Melbourne last month to begin preparing for 2025.
"I love this club and everybody involved in it," Simonsson said.
"I feel at home here, so it was an easy decision for me to stay and work towards where I want to be and where the club deserves to be."I'm very grateful to the club for sticking by me through my injury and I'm keen to give back to them and our fans with my performances over the next three years."
Parramatta still have four other players off contract next year.
Playmaker Daejarn Asi has spoken of the uncertainty surrounding his future, while Morgan Harper is also without a contract for next season.
Parramatta must also make a call on off-contract forwards Ofahiki Ogden and Makahesi Makatoa.
Fringe first-graders Zac Cini and Ky Rodwell have already left the club mid-season for England.
The Eels signed Zac Lomax on a big-money deal from St George Illawarra earlier in the year, while young gun Blaize Talagi is departing and signing with Penrith for the next three seasons.
Parramatta must find space in their top 30 for the likes of Charlie Guymer and other rising talent from their SG Ball squad.
Ryles faces a big year ahead on the roster front, with Simonsson's deal making him one of only four players officially locked in for 2026 and beyond.
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