The upset came after Autodata declared Mercedes the champion Wednesday using data gleaned from a "credible industry source" after neither automaker had reported their results on the industry's standard reporting day.
"I have great confidence that 2012 will be even better especially with the all-new BMW 3 Series arriving in the US in February with more new and refreshed models coming in the months after," Ludwig Willisch, chief executive officer of BMW of North America said in a statement.
With the champion of the past 11 years -- Toyota's Lexus -- hobbled by the fallout from Japan's devastating March 11 earthquake and tsunami, the two Teutonic giants went head-on to snatch the highly visible symbol of automotive supremacy.
Mercedes pulled ahead in November thanks to the launch of its new 2012 C-Class sedan and was expected to end up the victor.
But BMW regained the lead and claimed first place with a lead of just over 2,600 vehicles.
BMW reported Thursday its sales rose 12.6 per cent in 2011 to 247,907 after posting a 15 per cent gain in December.
Mercedes reported a 13.3 per cent gain to a record 245,231 vehicles sold in 2011 after a 28 per cent jump in December sales.
Lexus finished a distant third as 2011 sales dropped 13 per cent to 198,552.
BMW raised its incentive spending more than $200 to $3,694 per vehicle sold from November to December, while Mercedes' average spend remained virtually flat at $3,174, Edmunds.com found.
The average discount percentage on a new BMW in December was 11.2 per cent off the sticker price, compared to 9.5 per cent for a new Mercedes, the automotive website determined.
The bragging rights the crown brings can help in future sales.