Sunderland signed Charlton Athletic's Republic of Ireland midfielder Andy Reid just hours before the close of the January transfer window in a deal which could cost them £4million.
The north-east club, who are three points above the Premier League drop zone, have signed the 25-year-old on a three-and-a-half-year deal.
Sunderland manager and former Republic midfielder Roy Keane told the club's official website: 'Andy brings added quality to our side in an area that I felt needed to be strengthened.'
The clubs had announced earlier Thursday that defender Greg Halford would be making the opposite journey to the second-tier Championship club's south London home at The Valley.
Halford, 23, has made eight league appearances for Sunderland this season and Charlton manager Alan Pardew said: 'Part of doing business is to make sure you try to do something that's useful for your club.
'I lost Jermain Defoe in a similar situation when I was at West Ham United, and brought in Bobby Zamora.
'Hopefully, we can have similar success with Greg. He's coming here on loan and I think he's got a lot to prove.
'It didn't work out for him at Reading, it didn't work out for him at Sunderland, so I think he needs to be a success here, but I think he will be a massive asset for us.'
