James Bolton revealed that Pompey’s potential convinced him to move to the south coast.
The right-back has agreed to join the Blues on a three-year deal when his Shrewsbury contract expires at the end of the month.
He turned down the offer of a new contract with the Shropshire outfit, as well as attention from other clubs.
And Bolton is hoping to help his new side secure a spot back in the Championship after they narrowly missed out last term.
The 24-year-old said: “There’s been interest for a while, so it was always at the back of my mind that I could be coming here.
“This is a massive club. I think there were other teams interested, but I look at where Pompey can go and that excites me.
“I’ve moved up gradually throughout my career, so I’ve got to embrace this opportunity and try to do well here.
"I look at where Pompey can go and that excites me."
“We should definitely be fighting for promotion and know that anything else isn’t acceptable for this club.”
Bolton can offer versatility to the Blues back-line and also wants to contribute at the other end of the pitch.
He said: “I started out as a centre-half, but then got moved to the right and I don’t mind playing in either position.
“I’m quite fit and defend well, while also seeing myself as an attacking threat and I probably should score more goals.
“I do seem to get a few chances and hopefully I’ll be able to put a few more in the back of the net next season.”
Bolton opened his account for Shrewsbury with the winner in a League One contest at Fratton Park in January 2018.
He said: “It was a massive moment for me to score my first league goal and in what I felt was the biggest game of the season in front of so many fans.
“That was an occasion I’ll always remember and Craig MacGillivray was unreal that day, which is one of the reasons why he came here.”