Lee Brown has signed a two-year deal at Pompey.
The left-back moves to Fratton Park from Bristol Rovers after opting to leave the Memorial Stadium.
He will officially become a Blues player on July 1 upon the expiry of his Pirates deal.
But who is Kenny Jackett's fifth signing of the summer?
Here is the lowdown on him..
1. Lee Brown was born on August 10, 1990 in Farnborough. He primarily functions in a left-back role.
2. The defender joined QPR as a youngster. He penned his first professional contract at Loftus Road in July 2008 after helping the academy win the Youth Alliance title.
3. Brown spent time out on loan at Salisbury during the 2009-10 season and made 13 appearances at the Raymond McEnhill Stadium.
4. The left-back returned to QPR before the campaign was finished and was handed his Football League debut on April 24, 2010. Brown replaced Tamás Priskin in a 1-0 Championship victory at Barnsley.
Brown was subsequently offered a fresh one-year contract by boss Neil Warnock in 2009.
5. However, he failed to make another appearance for the Hoops and spent the majority of the 2009-10 campaign on loan Hayes & Yeading in the National League. He featured 29 times and scored three goals.
6. Brown was released by QPR in 2011 and subsequently moved to Bristol Rovers.
He quickly settled in at the Gas and became a regular starter.
7. Despite Rovers being relegated to non-league football in 2014, Brown remained at the club as opposed to jumping ship.
8. His loyalty was rewarded as the Pirates clinched back-to-back promotions to League One.
He also made three appearances for England C when his side were in the National League.
9. In total, Brown made 319 appearances for Rovers, registering 22 times. He was a favourite among the Gas fans for his consistency down the left flank.
10. Upon his departure, Rovers boss Darrell Clarke told the Bristol Post:
'He’s one of those players who had different options to go elsewhere but fought hard to get the club back in the league, a model pro in the changing rooms.
'He’ll go with our best wishes and the fans' best wishes.'
11. Speaking to The News, John Evely, who covers Pompey's League One rivals for the Bristol Post, said: 'There was disappointment among the fans after news of his leaving, because after seven seasons at the club he was part of the furniture at the Memorial Stadium.
'He can be replaced on the pitch but his presence on the training field and in the changing room is where he is really going to be missed.
'His departure was on his own terms and he was given a hero’s welcome when he left the field for the final time at the Memorial Stadium.
'He thinks he can play at a higher level. He has stated he has ambitions to play in the Championship but League One is probably about the right level for him.'