The Watford-based club have recruited the American international on secondment from USA Rugby for the new season.
Wyles, a full-back or wing who has won 10 caps, spent the 2006/2007 Premiership campaign at Franklin's Gardens.
Saracens rugby director Eddie Jones said: "Chris joins us on secondment from USA Rugby, who are looking to develop their players.
"He will also add further depth and competition to the Saracens squad, so this will be a mutually-beneficial agreement.
"Chris had a very good 2007 World Cup campaign in France. He is a player with a good kicking game and is strong in defence."
Wyles will soon come face to face with his former club as the two sides meet in the Premiership at Vicarage Road on September 27.
Saints begin their season on September 7 against Worcester Warriors, and wrap up their pre-season programme this weekend with a tough-looking double header.
On Friday, director of rugby Jim Mallinder takes his side to south Wales to take on Cardiff Blues (ko7.30pm), while on Sunday Italian side Benetton Treviso are the visitors to Franklin's Gardens (ko 3pm).
They are games that Mallinder is hoping will really stretch his side with the new campaign only days away.
"Both of the games this weekend will be good tests," said the director of rugby.
"Cardiff away will be tough because they are a very good side, but Treviso here will be a test as well.
"They are a European side that has been playing in European competition for a long time, so the games will test our squad but that is what we want before our first league game."
Again the Saints will be playing under the new Experimental Law Variations which are to be used this season.
So did Mallinder think the new laws made any difference in last weekend's 22-3 win over Western Force?
"It's hard to say," he said, "There is less mauling, there were a couple on Saturday, but there is a lot less.
"I do think the game is quicker, and I do think the ball is in play a lot more."