Pietersen's try and another from winger Gio Aplon in the first half at the new Otago Stadium in Dunedin proved enough to give the Stormers a sixth win in six matches on their first foray outside South Africa this year.
The Highlanders, who had lost just one match this season to stand second in the standings behind the Stormers, showed plenty of endeavour but were unable to breach the Stormers' blanket defence and scored only through two Chris Noakes penalties.
"It definitely wasn't easy," Stormers skipper Jean de Villiers said . "It was against a quality side and we were probably a bit lucky with some tries in the first half but we'll definitely take the win."
With two of the meanest defences in the competition on display, points should have been at a premium and the Highlanders will have been disappointed with the soft try they conceded in the 13th minute.
Centre De Villiers twice hacked at a loose ball after a turnover and Aplon won a footrace with the Highlanders cover defence to touch down.
There was nothing soft about Pietersen's effort 20 minutes later.
The 27-year-old started the move with a searing 25-metre break from inside his 22 and finished it with a perfectly executed chip-and-chase over the head of the last defender for a converted try that gave the Stormers a 15-3 lead.
Peter Grant, who alternated the kicking duties with Pietersen, scored the only points of the second half with two penalties and the white-shirted defenders held firm against wave after wave of Highlander attacks.
The visitors survived the loss of hooker Tiaan Liebenberg to the sin bin for 10 of the last 14 minutes and fittingly it was Pietersen's tackle that denied the Highlanders a consolation try just before the siren by forcing centre Tamati Ellison to brush the touchline with his boot.
Robert Ebersohn scored two tries as the
The outside centre's efforts were aided by 13 points from the boot of flyhalf Johan Goosen as the Cheetahs condemned the Lions to their fifth defeat in six matches. The Cheetahs took their record to three wins from seven games.
The first 20 minutes were characterised by ferocious defence from both teams but the Cheetahs broke the match wide open by scoring 16 points in 10 minutes.
Goosen kicked three penalties during the period as the Lions' discipline failed them while Ebersohn jinked past two would-be defenders on his way to a converted try to round off a sweeping backline move.
The Lions were looking increasingly rattled and five minutes before the break Ebersohn collected his second try when left wing Willie Le Roux ghosted through a gap to put his team mate into space with Ebersohn going over untouched for a converted score as the Cheetahs reached half-time holding a commanding 23-0 lead.
The Lions showed more endeavour in the second half but, despite dominating possession, they were thwarted by a highly efficient and composed defensive performance from the hosts.
The Gauteng-based Lions finally breached their opponent's defence in the 65th minute.
Replacement scrumhalf Michael Bondesio showed a good turn of pace as he sniped through a gap after a lineout before feeding flank Cobus Grobbelaar who crashed over for an unconverted try.
Four minutes later the Cheetahs extended their lead when replacement flyhalf Sias Ebersohn succeeded with a penalty kick.
Referee Jaco Peyper issued white cards for further consideration of television evidence by the citing commissioner after Bulls hooker Chiliboy Ralepelle and captain Pierre Spies accused the Crusaders of eye-gouging them in the ruck.
The Bulls won penalties for other ruck offences at the same time, with flyhalf Morne Steyn kicking both to bring the home side to within a point of the Crusaders at 13-12.
The Bulls then surged into the lead in the 44th minute when loosehead prop Dean Greyling threw an outrageous dummy before charging to the try-line.
Steyn converted to give the three-times champions a 19-13 lead.
Replacement centre Tom Taylor and Steyn exchanged penalties before the Bulls opened up a 32-16 lead with nine minutes remaining thanks to another penalty by Steyn and a try by centre Wynand Olivier, who was able to dot down the bouncing ball in the in-goal area .
The desperate Crusaders held sway in the last seven minutes as wing Sean Maitland's weaving run pulled apart the Bulls' defence and his fellow wing Zac Guildford showed good hands to take the try-scoring pass. Dan Carter's conversion closed the gap to 23-32.
Replacement fullback Tom Marshall burst through to score and Carter converted but was left to rue his 64th-minute penalty miss from the middle of the field.
The Bulls defended stoutly in the closing moments to hold off the seven-time champions and record their fourth victory in six games, moving to fourth on the overall standings.
The Crusaders' losing bonus point takes them to seventh overall.