Kanu's first-half goal won the FA Cup for Portsmouth against Cardiff in a low-key final at Wembley.
The Nigerian scrambled home the winner at the near post eight minutes before half-time after Cardiff keeper Peter Enckelman fumbled John Utaka's cross.
Cardiff enjoyed possession but rarely posed a serious threat, although Glenn Loovens had a goal ruled out for handball in first-half injury time.
And Portsmouth held on to claim the trophy for the first time since 1939.
It was a personal triumph for emotional Portsmouth boss Harry Redknapp as he enjoyed the highlight of his long managerial career when captain Sol Campbell lifted the trophy.
Underdogs Cardiff played with spirit, but did not have the quality to seriously disturb the Pompey defence, in which Campbell and Sylvain Distin were outstanding.
Cardiff boss Dave Jones did not gamble on Robbie Fowler, even as a substitute, after four months out with a hip problem - and his side did not feel his absence in a lively start.
Joe Ledley played in Paul Parry in the 12th minute but Portsmouth keeper David James made a crucial block to deny Cardiff the lead.
Kanu posted the warning signals for Cardiff as early as 21 minutes when he took a pass from Sulley Muntari in his stride and danced around keeper Enckelman, only to send his effort against the outside of the post with the goal unguarded.
He made no mistake eight minutes before the interval when Enckelman could only push out Utaka's whipped cross from the right flank and Kanu pounced to score.
Cardiff had more than held their own and almost provided an instant response when Parry raced clear down the left, but his cross stretched Kevin McNaughton as he arrived at the far post and the chance was gone.
And Bluebirds had a goal ruled out in first-half injury time when Pompey keeper James - who has form for high-profile mistakes in FA Cup finals - missed a corner, but Loovens handled before sending a looping finish into the net.
Loovens came to Cardiff's rescue after 52 minutes when Utaka set up Kanu again and he was forced to block a goal-bound shot with his chest.
Cardiff failed to apply consistent pressure to Portsmouth and boss Jones made a change after 61 minutes, sending on gifted 17-year-old prodigy Aaron Ramsey for Peter Whittingham.
It had been a desperately disappointing afternoon for the veteran Jimmy Floyd Hasselbaink, so it was no surprise when he was also hauled off with 20 minutes left and time running out for a Cardiff response.
David Nugent had come on as replacement for Utaka, and he forced Enckelman into a smart near-post save from a rising drive as Portsmouth attempted to kill the final off.
Loovens had proved to be a danger man for Cardiff at set-pieces and he sent a header bouncing just over the bar from Ramsey's corner after 79 minutes.
Cardiff's desire to push forward for an equaliser left them open to a counter-attack and Distin almost punished them with a run from the half-way line that was only halted by a fine tackle from Roger Johnson.
But it was Portsmouth's day as for once the favourites justified their tag in this season's unpredictable FA Cup.
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