Police are expecting high numbers in Edinburgh and, as such, Napoli fans have been banned to reduce the number of officers required.
For sporting fairness, Rangers fans have been banned from the return fixture next month.
A statement on Sunday read: "UEFA today announced that the UEFA Champions League tie between Rangers FC and SSC Napoli, originally to be played on Tuesday 13 September, has been rescheduled for Wednesday 14 September at 21.00CET. This is due to the severe limitations on police resources and organisational issues related to the ongoing events surrounding the national mourning for Her Majesty Queen Elizabeth II.
"In addition, it was agreed to also postpone the UEFA Youth League game between both teams from Tuesday 13 September to Wednesday 14 September at 15.00CET.
"Away fans will not be authorised at the games, and as a matter of sporting fairness, Rangers’ fans will not be authorised for the return legs in Naples.
"UEFA urges fans not to travel and to respect this extraordinary situation."
Rangers, who are hosting their first Champions League home game in 12 years, have said any home fans unable to attend the new date would be entitled to refunds and away tickets, previously held by Napoli supporters, would be put on sale.