This November, messages will appear on the front of City Hall in three languages - English, Irish and Ulster Scots.
Previously, only English and Irish signs were posted at Christmas.
However, at a committee meeting on Friday morning it was agreed to have three signs this year.
All summer, the parties at City Hall have been at loggerheads over bonfires, but common ground was found on the issue of Christmas.
Speaking in front of the building, Alliance councillor Michael Long said: "It may be August, but the spirit of Christmas has come early at City Hall.
"On this one we're going to have Irish, so it will be 'Nollaig Shona', then we will have 'Happy Christmas' - the original sign that we have - over in the centre and we're also going to have in Ulster Scots, 'Blythe Yuletide'.
"I think everybody'll be happy that we've actually managed to get an agreement across all the parties to get this done."
Sinn FÃ©in said it was happy to support the Ulster Scots sign going up for the first time.
Councillor Deirdre Hargey said: "Our position has always been to promote equality."
The new sign is expected to cost about Â£12,000.
There are 129 days until Christmas Day, but the signs are expected to go up at the end of November.
Belfast City councillors have put aside their differences over bonfires and reached an all-party agreement on Christmas signs at City Hall.