Striker Kanu has signed a new one-year deal at Portsmouth, while Sol Campbell has been confirmed as club captain for the new season.
Kanu, who was Portsmouth's top scorer last season, has the option of a further year depending on appearances.
Manager Harry Redknapp said: "I am pleased he has decided to stay.
"He was our top scorer last year after signing on a free transfer and now he has trained with us again and looked excellent."