The party, hosted by Rihanna's Clara Lionel Foundation, took place in Santa Monica, California, on Thursday 10 December.
Riri ensured she made a memorable entrance by choosing a champagne gold Christian Dior dress with matching puff sleeved coat, which she accessorised with diamonds and a silver manicure.
Jenner went for an ivory number by August Getty, which featured satin ribbon detailing and a striking fishtail train.
Both Rihanna and Jenner wore their hair loose and long and kept their makeup subtle with brown and matt pink lip shades.
There was also a hint of the bridal about Jada Pinkett Smith's white floor length Zuhair Murad dress with zip detailing.
Tickets to the Diamond Ball cost $3,000, reports Style News, and proceeds from the event benefitted the Clara Lionel Foundation, which Rihanna founded in 2012 in honor of her grandparents, Clara and Lionel Braithwaite.
The charity states on its website it "works to improve the quality of life for communities globally in the areas of health, education, arts and culture".
Scroll through the gallery below for more red carpet snaps: