Stephen Henderson has returned to Pompey in a loan deal from Nottingham Forest until the end of the season.
The 29-year-old goalkeeper made 27 appearances after joining the Blues in the summer of 2011, but financial problems saw him shipped out to West Ham eight months later.
Blues boss Kenny Jackett said: “I’m delighted to bring Stephen in. His experience will be vital in a young squad, as we enter the crucial final third of the season and push for the top six.”
"His experience will be vital in a young squad, as we enter the crucial final third of the season."
Henderson started his career at Aston Villa and then played for Bristol City prior to his first stint at Fratton Park.
The former Republic of Ireland under-21 international left the Hammers to join Charlton in 2014, moving to Forest two years later.