Clark Robertson was playing Championship football for Rotherham last season.
And the defender is in a hurry to get back to the second tier after completing his summer switch to Pompey.
The 27-year-old has put pen to paper on a two-year deal following the conclusion of his Millers contract.
Now he is looking forward to helping the Blues achieve success and put their 2020/21 disappointment behind them.
Robertson said: “I’m delighted – ever since the manager phoned me, it’s something that I’ve been really excited about.
“With the plans he’s got in place for this club going forward and also for me personally, I wanted to be a part of that.
“He put a presentation together of how he sees me playing and the style of football he wants suits my game. I can’t wait to get going.
"With the plans he’s got in place for this club going forward and also for me personally, I wanted to be a part of that."
“I’ve come down from the Championship and I want to get back there as soon as possible – hopefully I can do that with Pompey.
“The reason I came here is because I want another promotion under my belt and I know how to get out of this league.
“Everyone will be pushing together to try to get the club going in an upward trend again and it’s definitely an exciting time.
“My missus and I are buzzing about coming down to the south coast and looking forward to settling into life here.
“The atmosphere is always good at Fratton Park and I just can’t wait to play in front of a full ground – that’s something that really excites me.”
Robertson will be hoping to impress in the heart of the Blues defence after being converted from a full-back by a previous boss.
He explained: “The manager at Blackpool had seen me playing at centre-back for Scotland under-21s, so it stemmed from there.
“It’s been my main position ever since and I’m good on the ball, able to play out and also do the other side of the game by being strong and aggressive.”