Former Fulham midfielder Papa Bouba Diop has signed a one-year contract with the option of a further 12 months with West Ham.
The Senegal international was a free agent after being released by AEK Athens over the summer.
And Hammers manager Sam Allardyce has now completed a deal to take the former Fulham and Portsmouth midfielder to Upton Park.
The 33-year-old played for a West Ham development squad team against a Brentford XI on Tuesday before putting pen to paper.
Diop told the club's official website: "I am very happy today. I enjoyed playing again and it is good to be here to sign. I want to help West Ham go up and I hope we can be successful.
"English football is the best in the world. I have come here to work hard and give 100 per cent in every game I play for West Ham United. I want to show the people I am back again."