The Commerce Department said total retail sales fell 0.3 percent last month, the first decline in three months, after rising by an upwardly revised 1.8 percent in November. Sales in November were previously reported to have increased 1.3 percent.
Analysts polled by Reuters had forecast retail sales gaining 0.5 percent last month.
Compared to December 2008, sales rose 5.4 percent, but fell 6.2 percent for the whole of 2009.
Motor vehicle purchases fell 0.8 percent, while sales at electronics and appliance stores dropped 2.6 percent.
The data, coming in the wake of a report last week showing a surprise drop in non-farm payrolls in December, could add to worries that the economic expansion that started in the third quarter of 2008 could falter once government stimulus ends.
Stubbornly high unemployment remains the weakest link in the recovery from the worst economic downturn since the 1930s. Job worries are expected to constrain consumer spending, which normally accounts for more than two-thirds of economic activity.
Excluding motor vehicles and parts, retail sales fell 0.2 percent in December, the biggest decline since July, after rising 1.9 percent the prior month. Economists had expected a 0.3 percent increase.
Core retail sales, which excludes autos, gasoline and building materials, fell 0.3 percent after rising 0.9 percent in November.
(Reporting by Lucia Mutikani; Editing by Neil Stempleman)