Teenage goalkeeper Taylor Seymour has signed a one-year professional contract with Pompey.
The 18-year-old spent time on trial with the Blues last season, featuring in several academy and reserve matches.
Player development manager Mark Kelly said: “Taylor did really well when he came in and worked with the youth team.
"He needs to keep his head down and continue working hard to make sure he maintains that development."
“He’s a strong boy, who is willing to listen and learn. He showed a lot of positive attributes and so we decided to extend his stay with us.
“Now he needs to keep his head down and continue working hard to make sure he maintains that development.
“We want to make sure that he builds on those encouraging signs that we’ve already seen from him.”