Christian Burgess has penned a two-year extension to his Pompey contract.
The new deal will keep the 26-year-old centre-back at Fratton Park until the summer of 2020.
He has already made 103 appearances – and scored six goals – for the Blues since arriving on the south coast in June 2015.
“I’m delighted that everything’s been completed,” said Burgess. “It’s great to be able to commit to this club and I was always confident that I’d be here for a while longer.
"It’s great to be able to commit to this club and I was always confident that I’d be here for a while longer."
“I’ve been really lucky to get such great support from the fans here and I love playing in front of them. I appreciate their backing.
“But now it’s a case of business as usual – as it has been ever since talks started about a new deal.
“I’m just focusing on facing a tough Luton side in the FA Cup on Saturday and then trying to put things right in the league.”
Blues boss Kenny Jackett added: “I’m very pleased that we’ve agreed a new contract with Christian.
“He’s coming into his prime as a central defender and we will get the benefit of that over the next few years. I’m sure he’ll continue to do well for the club.”
Burgess appeared 45 times last season as Pompey secured the League Two title, scoring vital winning goals against both Leyton Orient and Luton.