The soap pulled in 45.9% of the total television audience, the BBC said, getting 10.9 million viewers on average and a peak of 11.9 million.
Yesterday's hour-long episode featured the murder of Archie Mitchell in the Queen Vic pub.
It was followed on the schedule by The Royle Family which attracted an audience of 10.2 million (42.5%).
Doctor Who chalked up 10 million viewers, which was a 42.2% audience share, and Gavin and Stacey 9.2 million (39.2%).
The BBC racked up nine of the top ten shows yesterday, including its broadcast of the Queen's speech which pulled in 5.6 million views.
ITV's Coronation Street came sixth with an audience of 7.9 million.
BBC One controller Jay Hunt said: "I am thrilled that BBC One continues to be the channel of choice for Christmas Day viewing. The range and variety of our line-up this year offered something for all audiences to enjoy."
More viewers tuned in to Christmas favourites in high definition, the most popular being Doctor Who with an audience of 343,000, and then The Gruffalo with 249,000.
This was up on last year when 120,000 watched Wallace and Gromit in HD.
BBC Director of Vision Jana Bennett said: "The BBC's commitment to providing the best possible viewing can be seen in these audience figures.
"Alongside great performances from BBC One and BBC Two I am particularly delighted that BBC HD's performance continues to go from strength to strength."
ITV1 is the most watched channel between 7 and 10pm, but BBC One is the most popular if this is extended to 6 to 10.30pm.
A spokesman said: "ITV1 has had a successful 2009, in which it has consolidated its position as the UK's leading peak time broadcaster and dominated the year's most watched programmes, particularly in entertainment and drama - with the channel having shown the top seven new dramas this year.
"After a fantastic autumn for ITV1, we are pleased that viewers enjoyed a broad range of Christmas programming across all channels."
The broadcaster said that Coronation Street beat BBC's Strictly Come Dancing, with an average of 7.9 million viewers compared to 6.8 million.
More people watched Emmerdale than last year, which drew in an average of 5.2 million compared to 4.8 million in 2008.
ITV1's audience share across the day was up to 19% from 17% last year, a spokesman said.
But BBC One was dominant, drawing in 30.8% of viewers.
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