It was announced on Friday that the England international would join the Sharks in Durban from January 1, 2015.
In a press release on their official website, Saracens said they had "reluctantly released" Botha to the Durban-based franchise.
“Mouritz has been a massive part of our squad and our culture for the past five-and-a-half seasons, and we are very sorry to see him leave. However, this is a great opportunity to play for one of the top teams in the Super 15, and we wish him, Natasha and young Joshua well," commented Mark McCall, Saracens' Director of Rugby.
Botha, who was born in Vryheid, KwaZulu-Natal, helped Saracens win the 2011 English Premiership.
He made his debut for England off the bench, in their 23–19 victory over Wales ahead of the Rugby World Cup in 2011.
He also featured for England in 2012 in both the Six Nations and in all three Test matches on their tour of South Africa, starting the first two and coming off the bench for the third. He has since accumulated over 110 caps for Saracens as well as making a total of 10 Test match appearances for England.
Commenting on his decision to move back to his native country, the 32-year-old said: "Saracens will always be important to me, and it’s difficult to leave so many friends in what remains a unique sporting environment, but the Sharks are trying to build something special in Durban. This will be a great rugby challenge for me, and a great adventure for my young family.”