The 22-year-old back-row forward follows Alan Solomons, the club's head coach, and Omar Mouneimne, their defence coach, who arrived last month from the Southern Kings in the Eastern Cape.
He is yet another player who could qualify for Scotland in three years' time because he is not yet tied to the country of his birth, but he has agreed a two-year deal which will potentially leave his options open at the end of that period should he establish himself at elite level.
In the short term, what is vital for the club is that, like Mouneimne, he is clearly an individual in whom Solomons has substantial confidence to set and maintain the standards he seeks to introduce in overhauling what has been a struggling club.
"This signing is fantastic news for the club: Cornell is the complete package," the head coach said yesterday. "He's very strong physically, is an exceptionally good carrier, has very good skills and is a powerful and confrontational defender.
"It was universally accepted that he was an absolute star in his first Super Rugby season. He's a fantastic player and we're delighted that he's coming here."
Solomons has admitted that the timing of his arrival in Edinburgh has restricted his involvement in rebuilding the squad. Yet he has made a series of interesting moves in recent days having offered loans to Joaquin Dominguez, a 26-year-old Argentine, and Alex Blair, younger brother of the former Scotland captain Mike, who has earned a second chance to establish himself in the professional game.
The recruitment of du Preez looks far and away the most immediately significant, though, the nature of the deal reflecting the fact that Solomons is bringing in someone whose qualities he knows well rather than relying on the counsel of others and therefore feeling the need to check things out before making a longer commitment.
At 6ft 4in and 17st, the youngster certainly cuts an imposing figure and he looks set to add to Edinburgh's already formidable finishing power since nine tries in 19 provincial games for Eastern Province helped earn him his place in the Southern Kings side and he ran in five more during their Super Rugby campaign.
Not least because it potentially widens his international prospects, du Preez is entitled to express delight at the latest chance Solomons has given him, then.
"I'm really excited about joining up with the squad," he said. "The decision to move was easy, especially when you look at the quality competitions that the club plays in week in, week out, taking on some of the best players in the world, all over Europe.
"I have a very good relationship with Alan and Omar, who've had a huge influence on my career and in my joining the club. They believe in me and I believe in their systems and what they want to achieve. I'm really looking forward to this awesome opportunity."