Trbojevic made his return from concussion in Manly's golden-point loss to Canberra last Saturday night, after suffering three separate head knocks last season.
Off contract at the end of this year, the former NSW State of Origin captain had been expected to extend at the Sea Eagles before the series of blows left him considering his future.
However the 32-year-old and Manly officials have since agreed to a new deal for 2027, with the forward having taken a pay cut from his previous contract signed in 2019.
AAP understands Trbojevic will have until round 10 to activate the deal as he gauges his return to play, but it's expected Manly would offer more time if it was needed.
"I just want to see how I go," Trbojevic told AAP ahead of Sunday's home clash with Newcastle.
"I did a lot of work in the pre-season, and a lot of contact.
"Last year was a bit disappointing with how it all went. Obviously just getting knocked out every second week was disappointing.
"So I want to see how I go and I want it to work for both parties. ... I was always going to play this year, so it doesn't change anything."
If Trbojevic gets through this season unscathed, he is set to become Manly's fifth-most capped player in history.
Playing on into next year would allow him to overtake Cliff Lyons and Steve Menzies in matches for the Sea Eagles as a single entity, and move into the club's top three.
The lock has long made clear he could never see himself playing for another club, with the 13-Test veteran all but certain to finish his career in maroon and white.
The situation comes after younger brother Tom Trbojevic also inked a one-year extension with Manly at the end of last year, with the new captain a free agent again in November.
In an interview with AAP last month, Jake Trbojevic admitted the prospect of life after football was "scary", given he'd been in the Manly system since under-12s.
He has spoken about trying to be smarter in his tackle technique to avoid any further concussion, while also adopting a new protective headgear this season.
"The first game it was good, I don't feel like I had a head knock, so that's a positive," Trbojevic said.
"It's good. I really like it. It's quite padded. It's good for me mentally, and hopefully it's good for me physically too.
"It gives me confidence. It has some research behind it, so it gives me great confidence to give it a go and it's been great for me training in the off-season."
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