Eddie Jones says he is determined to help make Saracens one of the leading clubs in Europe after resuming his role as a consultant at Vicarage Road.
Jones is helping South Africa prepare for the World Cup in France
The former Australia coach worked at Saracens last year and will start his new job on 30 July.
"Saracens have got great potential and the ambition to be a leading club in England and in Europe," he said.
"I am looking forward to over the course of the next few years working with the club to realise that goal."
The news of Jones's move back to Saracens was broken by BBC Sport in May.
Jones, who is currently helping South Africa prepare for their World Cup campaign, was instrumental in helping Saracens avoid relegation from the Premiership last year.
He took over at Super 14 side Queensland but resigned in May after the Reds finished bottom of the table.
At Saracens, Jones will concentrate on areas such as recuitment, with rugby director Alan Gaffney remaining in charge of all rugby and playing matters.
"Eddie will have a similar consultancy role to that which he has done in the past few years, but Alan will remain in control of all rugby issues," Saracens chief executive Mark Sinderberry added on the club'swebsite.
"What we are asking Eddie to do is focus on areas of the club such as the recruitment of players and for him to keep an eye on developments in the game so that Saracens keep up to date with what is happening across the world.
"He will also work with the academy, and of course with his experience of international rugby, Eddie will be an invaluable resource to the coaching staff when he is required."