The 34-year-old has enjoyed a successful spell in France after winning the 2017 French title.
He also reached the Champions Cup final but he has decided to return to Allianz Park after spending three years in France.
Strettle has signed a one-year deal with Saracens and the former England international admits he cannot wait to return.
"I already have some unforgettable memories at Saracens - they have always had a place in my heart," Strettle told Saracens' official website:
"An opportunity arose in France which I took as a fresh challenge, but now can't wait to come home and hopefully make some more great memories.
"Some of my best friends are at Saracens, so I can't wait to get back out on the field and be a part of the same team with them again."