The Queen and Duke of Edinburgh are at the royal estate in Sandringham, Norfolk and will be present for the sermon at St Mary Magdalene Church.
Her Christmas speech, to be broadcast at 15:00 GMT, will pay tribute to the UK's Olympic and Paralympic athletes.
The address will, for the first time, be broadcast in 3D.
The Queen traditionally spends the festive period with her family at Sandringham, but this year will not be joined by the Duke and Duchess of Cambridge, who are with the duchess's family in Bucklebury, Berkshire.
Earlier this month, it was announced that Prince William and Catherine are expecting their first child, after the duchess was admitted to hospital following an acute bout of morning sickness.
Prince Harry will also be absent from the celebrations, as he is currently serving as an Apache helicopter pilot with the Army Air Corps in Afghanistan.
'Excitement and drama'A Buckingham Palace spokeswoman said the Queen's self-penned Christmas speech, broadcast to the UK and Commonwealth, will focus on "service, achievement and the spirit of togetherness".
She will hail the "splendid summer of sport" in the pre-recorded address and will highlight how the sportsmen and women allowed spectators to feel part of the "excitement and drama".
The Queen will say: "As London hosted a splendid summer of sport, all those who saw the achievement and courage at the Olympic and Paralympic Games were further inspired by the skill, dedication, training and teamwork of our athletes."
The Queen had her own starring role in the London Olympics, declaring them officially open after appearing to parachute into the stadium with James Bond - played by current 007 Daniel Craig.
Behind-the-scenes footage of the Christmas message, made on 7 December, has been released showing the Queen meeting senior staff from Sky News which produced the broadcast this year.
In other footage she wears 3D glasses as she watches part of the broadcast, which will be transmitted on both TV and radio at 15:00 GMT.
Her use of 3D technology comes 80 years after George V first broadcast a Christmas speech on the radio and started the 25 December tradition.
It has been an eventful year for the royal family, with the Queen celebrating her Diamond Jubilee in June, marked with celebrations in the UK and Commonwealth.
She also became the first British monarch to reach a 65th wedding anniversary.
But there were health scares, with Prince Philip, 91, forced to miss some key events during the Jubilee celebrations after being taken to hospital with a bladder infection.
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The Queen, pictured with the PM on a visit to Downing Street in June 2011 The Queen is expected to attend a cabinet meeting in Downing Street for the first time.