"It's great news that Glen's decided to sign a new contract," Pompey boss Tony Adams told the club's official website.
"I'm delighted to have him here. I want him here for a long time.
"This is a good place for him. He's got back in the England squad since he came here.
"Glen's applied himself really well. He's always desperate to play and gets frustrated when he can't.
"He's been very good for this club and this club's been very good for him."