Pompey will complete the signing of Bryn Morris on Monday.
Kenny Jackett confirmed the midfielder is set to arrive at Fratton Park from Shrewsbury.
The Blues have beaten promotion rivals Luton to the 22-year-old’s signature.
Morris arrives after impressing in a loan spell at Wycombe over the first half of the campaign.
Jackett said: ‘It’s been agreed and he will come down on Monday to sign.
‘We’ve needed some players in midfield.
‘Bryn will come into a midfield along with Andy (Cannon) which has needed some competition with Ben Thompson returning to Millwall.
‘They are both the right age to come to an excellent club like Portsmouth.’