Further ticket arrangements for Ulster Rugby fans will be announced in the coming days once more information becomes available.
Nigel Wray, Saracens chairman, said: "We look forward to playing this important match at the home of English rugby, a ground that many of our players know extremely well.
"It is absolutely clear that people want to see big teams playing big matches at big stadiums, and that is precisely what we will deliver at Twickenham."
He continued: "We did consider the option of playing this showpiece match at Allianz Park, our brand new home stadium in NW4, but, in consultation with local residents and our partners at the London Borough of Barnet, we have decided to settle at the new venue before applying to stage a one-off event with a larger capacity."
