The decrease of $1.5 billion included a gain of $1.6 billion in exports, which was slightly offset by a $0.1 billion increase in imports.
Economists had expected the trade gap to go the other way, predicting a slight gain.
Among major trading partners, the trade gap with China dropped from $27.8 billion in January to $23.4 billion in February.
With the Organization of Petroleum Exporting Countries the gap decreased from $6.4 billion to $3.6 billion.
The trade gap with the European Union rose from $8.6 billion to $8.8 billion, and with Japan it fell from $6.1 billion to $5.9 billion, the bureau said.