The 36-year-old Miller was snapped up Delhi Capitals for R3.7million having previously represented Gujarat Titans and Punjab Kings in the T20 franchise tournament.
Miller will be joined at the Capitals by Ngidi, also purchased for R3.7million, while fellow fast bowler Nortje will play for Lucknow Super Giants at the same price.
De Kock was bought by Mumbai Indians for R1.9million with the wicketkeeper-batter having been released by the Kolkata Knight Riders.
The four players will join 12 other South Africans in the IPL next year that were retained by their franchises from last season.
Cameron Green became the most expensive overseas player ever bought at an IPL auction when the Knight Riders splashed R55million on the Australia all-rounder.
South Africans retained at IPL franchises:
Dewald Brevis (Chennai Super Kings)
Tristan Stubbs (Delhi Capitals)
Kagiso Rabada (Gujarat Titans)
Aiden Markram (Lucknow Super Giants)
Matthew Breetzke (Lucknow Super Giants)
Ryan Rickelton (Mumbai Indians)
Corbin Bosch (Mumbai Indians)
Marco Jansen (Punjab Kings)
Donovan Ferreira (Rajasthan Royals)
Lhuan-dre Pretorius (Rajasthan Royals)
Kwena Maphaka (Rajasthan Royals)
Heinrick Klaasen (Sunrisers Hyderabad)
Quinton de Kock praised Ryan Rickleton's ability to adjust to the No 3 role and believes the rest of the lineup will need to show similar levels of adaptability if the Proteas are to win the T20 World Cup in India.
David Miller has been declared fit to join the Proteas squad ahead of their departure to the T20 World Cup after recovering from an abductor muscle injury sustained during the SA20.
Quinton de Kock produced a stunning innings at SuperSport Park as South Africa chased down a huge target to beat West Indies by seven wickets in the second T20I in Centurion, sealing the series with a match to spare.
Shai Hope and Lungi Ngidi delivered landmark performances as Pretoria Capitals beat Durban's Super Giants by 15 runs in a dramatic SA20 clash at Kingsmead.
