The big right-hander defied the Australian bowlers and a Glenn McGrath ball to the ribs to ensure a solid, if not daunting, total on a good batting wicket on Friday.
Pietersen's 82 from 91 balls was the mainstay of England's total from 50 overs after they won the toss and elected to bat in the first match of the series, also featuring New Zealand.
England were in early trouble at 3-73 and didn't pick up what was a pedestrian run rate until Pietersen went after the leg-spin of rookie all-rounder Cameron White in the 34th and 36th overs.
Pietersen, one of few England players to come out of the Ashes debacle with his reputation intact, lofted White over long off for six to bring up his 50, from 63 balls.
He then hit successive sixes in White's next over to finally give England fans something to get excited about.
Pietersen, who eventually holed out to Andrew Symonds on the mid-on boundary from the bowling of Stuart Clark, had useful support from Paul Collingwood (43) and Andrew Flintoff, who hit out late to make an entertaining 47 not out from 38 balls.
Although he played some glorious shots, particularly straight down the ground, and fell in the chase for quick runs late on, Pietersen also looked uncomfortable after taking a rising McGrath delivery in the ribs in the 40th over.
The England batsman had advanced at McGrath, a tactic he used regularly to counter the length of the Australian bowlers, but fell heavily after being struck and appeared restricted afterwards.
Unfortunately, Pietersen's dismissal sparked yet another England collapse as they lost 3-5 and squandered the chance for a bigger total, while Ricky Ponting took a stunning catch to remove Jon Lewis in the penultimate over.
Left-armer Mitchell Johnson, 12th man for all five Ashes Tests, was impressive with 2-34 from his 10 overs.
Nathan Bracken (3-44) put the home side on top early, claiming the wickets of Andrew Strauss, whose lean run on tour continued when he was brilliantly caught by Matthew Hayden, and England captain Michael Vaughan.
Vaughan, in his first One-day international since returning from knee surgery, was looking in good touch.
He advanced slightly and attempted to drive Bracken, but only got a thick edge into slips and Hayden moved quickly to his right to take a neat catch.
After Ian Bell (15) then fell to Johnson, Pietersen and Collingwood put on 95, before a McGrath change of pace claimed the latter with the second ball of the veteran's second spell.
McGrath had been brought back on to replace White, who had gone for 27 runs in just three overs as Pietersen cut loose.