The 23-year-old arrives following his release by Huddersfield at the end of last season and will compete with Will Norris for the No1 jersey at Fratton Park.
His move means the Blues have now signed 12 players during the current transfer window, with a new No8/10 also wanted by John Mousinho before September.
However, Pompey haven’t been the only ones adding to their squad over the past week. Here’s what strengthening their League One rivals have been doing since Sunday.
1. League One transfers
From left: Tayo Edun, Terry Taylor, Ryan Schofield and Kell Watts Photo: Getty Images
2. Dale Taylor (Wycombe)
Club just left: Nottingham Forest Transfer details: Loan deal. Photo: Nathan Stirk
3. Max Watters (Barnsley)
Club just left: Cardiff Transfer details: Permanent move. Undisclosed fee. Photo: Dan Istitene
4. Taylor Perry (Shrewsbury)
Club just left: Wolves. Transfer details: Free transfer. Photo: Alex Pantling