But the kick drifted to the right of the near post and Bulls players, coaches and supporters sighed with relief after salvaging a draw from a game they appeared destined to lose.
Bulls had levelled two minutes before time with substitute Tian Schoeman slotting a much more difficult penalty than the one Pietersen fluffed.
It was the only miss at goal during a scrappy contest by Pietersen, who kicked three penalties and converted a try from full-back Willie le Roux.
Bulls full-back and official man of the match Warrick Gelant scored a try, fly-half Francois Brummer kicked a conversion, a penalty and a drop goal and Schoeman slotted a penalty.
Sharks, who beat Southern Kings, the Argentine Jaguares and Western Stormers in earlier rounds, are six points clear of Golden Lions at the top of the Africa 2 standings.
Three-time Super Rugby champions Bulls climbed one place to second in the Africa 1 table, four points adrift of 2015 quarter-finalists Stormers.
"It was a game we could have won," said Sharks prop and skipper Tendai 'The Beast' Mtawarira. "We fought back well after battling in the opening half."
Bulls hooker and skipper Adriaan Strauss responded: "We will take a draw after the situation we found ourselves in. It was a typically physical South African derby."
A pre-match downpour meant a slippery ball and pitch and there were many handling errors and turnovers in a game where neither side reached top form.
New Zealand referee Glen Jackson was kept busy, awarding many penalties, especially during scrums.
Bulls led 13-6 at half-time only to fall behind as Sharks, thanks to a try created and finished by Le Roux, scored 10 unanswered second-half points.
An offside call allowed Schoeman to equalise and then came the miss that will haunt Pietersen for some time.
Bulls 16 (Warrick Gelant try; Francois Brummer conversion, penalty, dropped goal, Tian Schoeman penalty), Sharks 16 (Willie le Roux try; Joe Pietersen converson, 3 penalties). HT: 13-6.
-News.com.au
