The Super Rugby star will make the move to Rodney Parade from the Free State Cheetahs for the start of next season.
The 30-year-old made his Super Rugby bow for the South African side against Western Force in 2009 whilst also playing provincial rugby for the Griquas. He faced the Lions in the same year when he was selected for the Royal XV.
Pretorious moved to the Waratahs for two years, but returned to his native South Africa to resume his career with the Cheetahs. Speaking after putting pen to paper, Pretorius commented: “I am delighted to have signed for the Dragons.
“They have a great group of players along with fantastic facilities and coaches, so I am looking forward to joining up with the squad. I feel that it is an exciting time to be involved and I am looking forward to seeing where we can go as a club.”
The Dragons European Challenge Cup form has revitalised a season in which they have suffered league woes. They resume their LV=Cup campaign this weekend when they welcome Exeter Chiefs to Rodney Parade.
Lyn Jones, director of rugby added: “We are delighted that Sarel has made the move to the Dragons. He is a very experienced player and it’s that wealth of experience and ability that we need amongst our young squad.
“He is an exciting signing for us and is a great fit and I look forward to working with him next season.”