The World Cup winner fractured a bone in his right hand playing for the Bulls in Saturday's Super 14 clash with the Cheetahs in Bloemfontein.
Bulls team doctor Tommie Smook confirmed on Sunday that Du Preez will be out of action for six weeks and will also have to undergo a minor operation.
"Fourie suffered a break to his right hand and he will have surgery on the hand to insert a pin," said Smook. "He will be out for up to six weeks."
Du Preez will likely recover in time for the Springboks' Tri-Nations campaign, which gets under way on July 5 against New Zealand in Wellington.