The French attacker has agreed a deal at Fratton Park for the second half of the campaign, subject to FA and EFL approval.
The 22-year-old is viewed as the man who can bring additional depth and quality to the final third of the pitch, as John Mousinho’s side bid for Championship survival.
There were fears today over the move failing to reach a conclusion, with an agreement place between the two clubs.
That related to the Home Office’s relaxed Governing Body Endorsement (GBE) criteria for overseas players, but those issues have now been resolved allowing the agreement to be sealed.
Aouchiche has scored twice in 38 appearances for Sunderland, featuring 10 times for the high-flying Championship side this season. That included a start in the 1-1 win for the Black Cats at the Stadium of Light on January 5.
The former Paris St Germain man becomes Pompey’s sixth January signing and second capture of the day, after a deal was sealed for Rotherham’s Cohen Bramall.
Loanees Rob Atkinson and Isaac Hayden along with with permanent Aussie signings Hayden Matthews and Thomas Waddingham are the Blues’ other signings this month.
