The 35-year-old ex-England batsman, who made his highest Twenty20 score with 115 not out from 66 balls on Wednesday, hit seven sixes in 100 from 45 balls.
It took Durban-based Dolphins to their 168 target as they beat the Knights by nine wickets with 20 balls to spare.
Pietersen will appear in two more games for the Dolphins before heading to Australia for the Big Bash League.
The South Africa-born batsman last played for England in the 2013-14 Ashes whitewash in Australia and was told in March that year that he was not part of England's future plans.
Meanwhile, there was a new Twenty20 world record in New Zealand as former Kiwi opening batsman Peter Fulton claimed five outfield catches for his Canterbury province against Northern Districts in their domestic Super Smash T20 league.
Listen to BBC World Service's Stumped programme, featuring an interview with Kevin Pietersen.
Kevin Pietersen smashed a second successive unbeaten hundred in South Africa's Ram Slam T20 event.