Defence Secretary Ben Wallace praised the "selflessness" of the armed forces personnel and their families.
Around 11,000 Army, Royal Navy and Royal Air Force personnel are serving on 35 overseas operations in countries including Iraq and Afghanistan.
The troops have already begun sending messages to loved ones, the Ministry of Defence said.
More than 1,000 personnel are stationed in the Falkland Islands in the South Atlantic, while in the Caribbean the air force remains on alert over the hurricane season, the MoD added.
The Royal Navy will have 14 ships at sea on Christmas Day, including HMS Defender, which was used to seize £3.3m of crystal meth in the Arabian Sea on Monday.
"Over the festive period we should all take a moment to be grateful for the selflessness of our armed forces personnel and their families," Mr Wallace said.
"This Christmas, like any other day, our servicemen and women will be displaying their unique professionalism around the world and at home."
Mr Wallace, who was an officer in the Scots Guards before entering politics, said he knew what it was like to work away from home over Christmas and New Year.
Meanwhile, the MoD has donated more than 14,000 unused ration packs to food waste charity FareShare, which will distribute the packages to charities running homeless outreach programmes in London over the Christmas period.
The packages do not need to be refrigerated and include ingredients for breakfasts, lunches and dinners such as porridge, sausages, pasta and baked beans.
On Thursday, the defence secretary confirmed that there was a shortfall of funding in the MoD's budget.
The armed forces were given an extra £2.2bn in September's spending review when the chancellor announced a 2.6% increase in defence funding in 2020-21.
But a defence spending squeeze between 2010 and 2015 has prompted questions about whether the UK is equipped to meet future security threats.
In February, the House of Commons' spending watchdog reported the MoD faced a £7bn black hole in its 10-year-plan to equip the armed forces.
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