The tie had been due to be played on Thursday evening but was postponed due to police resourcing issues related to the Queen's death.
There were concerns Arsenal may have had to forfeit the match if an alternative date could not be found, but the Premier League has agreed to postpone the Gunners' match against Manchester City which had been scheduled for October 19.
The match will now kick off at 6pm on October 20, UEFA said in a statement.
"UEFA would like to thank the Premier League and the clubs concerned for their flexibility and co-operation in the rescheduling of the UEFA Europa League match which had been postponed due to the impossibility for local police forces to guarantee its secure staging," the statement concluded.
The Premier League said that a new date for the Arsenal v Manchester City match would be announced in due course.
The league already faces a challenge to rearrange all of last weekend's matches, which were postponed as a mark of respect to the Queen, plus three games due to be played this weekend - Brighton v Crystal Palace, Manchester United v Leeds and Chelsea v Liverpool.
Those games have been postponed due to police resourcing issues, as the authorities prepare for the Queen's state funeral on Monday. Brighton v Palace had already been postponed prior to the Queen's death due to a planned rail strike. Even though the industrial action has now been called off, the game remains postponed for policing reasons.
Finding available slots in the calendar for all these matches is especially challenging this season because of the staging of the World Cup in Qatar in November and December.
Senior sources within the game have suggested one option which may have to be looked at is to scrap FA Cup third and fourth-round replays for the third season in a row to free up two midweek slots in January and February to alleviate the congestion, but it is recognised that these matches can be of enormous financial and sporting benefit, particularly to lower-league clubs.
The Premier League confirmed its plans to pay tribute to the Queen at this weekend's matches which are still going ahead.
Fans will be asked to join a minute's silence, which will be followed by the national anthem.
Big screens and perimeter boards will pay tribute to the Queen and flags at stadia will fly at half-mast.
Fans will also be invited to applaud at the 70-minute mark, in recognition of the Queen's 70-year reign.
The start of the new Barclays Women's Super League season was called off last weekend after all English football fixtures were postponed as a mark of respect following the Queen's death.
Arsenal will now open the campaign at home to Brighton on Friday evening, having originally been set to be away at Manchester City for their first game.
The dates for all of the rescheduled fixtures will be announced in due course.
Arsenal head coach Jonas Eidevall would like to see all of those games played across one weekend, rather than facing up to a skewed table.
"My opinion, but I don't think that is going to matter, is that in the WSL that you would play all the games from this round being postponed at the same date," the Swede said.
"So (then) you don't create a league table where some players teams have played 10 and some teams have played 11, you play on different sides of the transfer window and so on.
"I don't think anyone will take that into account, but for me when I look from that from just trying to make it fair, it is really important that the competition is fair to all teams. I would do it that way."