The U.S. Commerce Department released the trade data on Friday. The U.S. trade deficit widened to $43.36 billion in December from a deficit of $42.23 billion in November. November's figure was revised up from a deficit of $42.37 billion.
Analysts had expected a trade deficit of $43.0 billion.
The rise of a deficit was driven by a drop in exports. A stronger U.S. dollar and a weak demand abroad weighed on exports.
Exports fell by 0.3% in December, while imports increased by 0.3%.
In 2015 as whole, the trade deficit rose by 4.6% to $531.5 billion compared with the previous year. Exports dropped 4.8% in 2015, while imports declined 3.1%.