The Dolphins have secured Selwyn Cobbo until the end of 2031, extending his existing contract by four seasons.
The 24-year-old had previously re-signed through next year, allowing rival clubs to approach him from November 1.
The new deal is reportedly worth about $800,000 per season.
Cobbo's outstanding form has made him a Queensland starter and a likely Kangaroos selection for the October-November World Cup.
He has also been important to the Dolphins' finals push, with the club receiving a preliminary-final bye before facing either the Sydney Roosters or Cronulla Sharks.
"Selwyn has made an immediate impact since joining the Dolphins and what he has been able to produce in his first season at the club has been remarkable," CEO Terry Reader said.
Reader added, "At just 24 years of age we know there is still plenty of great football ahead of him, and we're excited that will be in a Dolphins jersey."
Cobbo's extension followed Kulikefu Finefeuiaki's commitment through 2029.
The deals reduce the Dolphins' off-contract list but increase salary-cap pressure, with Jack Bostock, Herbie Farnworth and Hamiso Tabuai-Fidow among those off contract after 2028.
At least one marquee player is widely expected to leave, although the group reportedly wants to stay together.
Bostock has been linked with St George Illawarra, while Farnworth has been mentioned as a possible Sydney Roosters target.