The 30-year-old was left out of the national squad to face Pakistan in the upcoming Twenty20 and one-day series as England were keen for him to find some form at The Oval ahead of this winter's tour of Australia.
As a coach at Surrey I can tell you how excited everyone is at the club to have Pietersen in the ranks, and it will give the fans a big boost to end the season, too.
This is more about England than about Surrey - everyone wants England to win the Ashes and to see KP back in form and that is the most important thing.
Pietersen is due to play in all four of Surrey's remaining fixtures and it is a big fillip for the club - and also for England with the Ashes coming up in November.
There is no point in having KP on board unless he is playing, and he knows that he will get a lot of cricket to end the season.
Surrey are losing Steven Davies to the England set-up so he will effectively just replace him. He won't keep anyone out.
I think Pietersen will have a huge impact, not only with his presence around the side, but also in terms of bringing in a few more spectators.
But, of course, the main reason why the deal has been agreed is for Pietersen to score lots of runs and get back into form for England.
It was always going to be a fairly controversial issue for coach Andy Flower and captain Andrew Strauss, with it being KP's first time away from the national side through selection reasons alone.
This is very much a short-term deal for Surrey and for Pietersen, but if he hits the ground running in Australia then it will go down as being a superb deal for all parties.
No one doubts Pietersen's qualities, but this is the perfect opportunity for him to show everyone that he is willing to guts it out on the county circuit to justify his selection.
It is a soul-destroying thing to be as out of nick as KP is right now, but a few good knocks for the Brown Caps will see him back where he was before his Achilles injury.
England will be watching how the batsman gets on down at The Oval for the remainder of the season, and everyone who has the country's best interests at heart will be hoping that Pietersen regains his mojo.
Courtesy: Yahoo! Eurosport UK