More than half of the decline came in the last month of the year, the bureau said. The trade deficit fell $10.1 billion November to December to $38.5 billion for the month.
The final month's decline was a surprise. Economists had predicted the deficit would drop to about $46 billion.
Exports in December rose $3.9 billion, climbing from $182.5 billion to $186.4 billion, while imports dropped $6.2 billion, sliding from $231.1 billion to $224.9 billion, the bureau said.
The bureau said exports rose sharply in industrial supplies and materials and foods and feeds. Those categories offset declining exports in capital goods, automobiles and consumer goods.
Similarly, the drop in imports month-to-month was led by a decline in industrial supplies, automobile and capital goods.
Among major trading partners, the trade gap with China dropped from $29 billion to $24.5 billion in December. The decline in the trade gap with the Organization of Petroleum Exporting Countries fell from $6.6 billion to $3.4 billion, November to December, a figure down from $8.6 billion in October.
The trade deficit widened with only one major trading partner in December: Canada, where the deficit rose from $2.8 billion to $3.6 billion.