Having patched up his differences with Pompey chairman Milan Mandaric, Redknapp is keen to consolidate the club's position in The Premiership and will see Griffin as a valuable acquisition to his backline.
Griffin has signed a four-year contract with the South Coast club, having made 90 appearances in his time at St James' Park, and arrives on a free transfer.
The 25-year-old full-back started his career at Stoke City, before a series of excellent displays won him a move to the top-flight.
However, having failed to ever establish himself as a first team regular under Sir Bobby Robson's tenure, Griffin will be keen to prove himself at Fratton Park.
