The Manly Sea Eagles have announced the contract extension of prop Addin Fonua-Blake for a further two years through to the end of the 2020 season.

The 21-year-old made his NRL debut in 2016, playing 14 matches for the Sea Eagles in his inaugural season with a further 21 appearances for the club this year.

"Addin has taken his game to another level and has become a key component of our developing forward pack," Sea Eagles Head Coach Trent Barrett said.

Sea Eagles Chief Operating Officer Neil Bare said the extension was a great reward for Fonua-Blake as he heads into his first Telstra Premiership finals series this Saturday night.

"We are proud of Addin's development both on and off the field, and securing him longer term was a high priority for us," Bare said.

"Addin is maturing into one of our real leaders in the club, and with his young family, has settled well into life on the Northern Beaches."