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.
5. Carlos Mendes Gomes (Bolton)
Club just left: Luton Transfer details: Permanent move. Undisclosed fee. Photo: David Rogers
6. Sullay Kaikai (Cambridge United)
Club just left: MK Dons. Transfer details: Free transfer. Photo: Stu Forster
7. Andrew Dallas (Barnsley)
Club just left: Solihull Moors. Transfer details: Free transfer. Photo: Nathan Stirk
8. Finley Back (Carlisle United)
Club just left: Nottingham Forest. Transfer details: Loan. Photo: Pete Norton