Campbell, who joins as a free agent after ending his five-year spell with Arsenal last month, underwent a medical on Monday and trained with Portsmouth's squad on Tuesday before signing the deal.

The arrival of the England central defender, who will be 32 next month, represents a coup by Pompey manager Harry Redknapp, whose team narrowly avoided relegation last season.

Campbell, a former Tottenham Hotspur captain, won two league titles and three FA Cups with Arsenal. He scored in their Champions League final defeat by Barcelona in May.