The troops are working as usual for much of Christmas
Many of the 250 or so troops, mainly from the Royal Marines, spent Christmas morning at work in the streets and government buildings of the capital Kabul, while others were at the Bagram airbase about 40km (25 miles) north.
Army chiefs supplied some festive cheer - Christmas dinner, phone calls home and carol-singing with US troops.
Captain Andy Mason, at Bagram airbase, told BBC News that Christmas Day was a "normal operational day".
He said: "We've got patrols going out in Kabul, they're showing a presence within vehicles... we've also got guys here working in operation rooms, and carrying out their daily chores.
"That can be doing anything from doing their normal washing to even working out in the gym - I saw some guys this morning doing a PT session morning in the beautiful sunshine."
He added that despite the basic conditions in Afghanistan, some of the troops had managed to find presents to give each other.
"Sweets from the ration pack have been wrapped up, wrapped round with black masking tape and handed over - so the spirit of Christmas is here."
At lunchtime the troops had a Christmas party in a Bagram aircraft hangar, joining American allies in a US-style Christmas lunch of turkey, mashed potatoes and pumpkin pie.
Alcohol was not served because the troops were on duty.
Afterwards a group of the British troops took on a team of US soldiers in a game of American football, which ended in a draw.
Other soldiers told journalists they were missing their families, but hoped to see them fairly shortly and would speak to them later.
Captain Craig Marco said: "My family is in Zimbabwe and my girlfriend. I will tell them a Happy Christmas and I hope to see you soon."
Major Mark Bernett said: "I wish everybody at home a Merry Christmas. I hope you have a good time, I hope to see you soon."
Queen's message
The British peacekeeping troops have been in Afghanistan since Thursday, carrying out duties such as patrolling the streets, clearing landmines and beginning the rebuilding of the country's shattered infrastructure.
BBC correspondent Daniel Sandford said some troops were also at Kabul airport, which they were hoping to open up to bring in the international security assistance force next week.
He said the troops had received a fairly warm welcome from the Afghan people.
"You see a certain amount of open-jawed amazement when the British troops drive through the streets of Kabul - people aren't quite used to it yet and are very surprised to see them driving through.
"But by and large it's a big welcome - they tend to get waved at, with children smiling and running after their vehicles."
Another 1,500 or so British troops are due to be deployed in Afghanistan in coming weeks, as part of a multi-national security force which will eventually number up to 5,000.
In total, there are 22,000 British service men and woman spending Christmas overseas, in 30 countries.
Both the Queen and Prime Minister Tony Blair have sent the troops Christmas messages of goodwill.