 Car exports were hit particularly hard last month |
But it was the seventh consecutive month that Japan's exports exceeded its imports by value.
The world's second-largest economy had a trade surplus of 185.7bn yen, compared with a deficit last year.
"Japan's exports to key regions, including the US and Asia, were all down sharply due to sluggish demand," said finance ministry official Keisuke Kawanishi.
Imports dropped 41% from a year earlier.
The slowdown in Japan had been steeper than that experienced in the US or Europe, with the jobless rate reaching a record high.
But the country recently emerged from recession due to the government's massive stimulus package.
Japan's car exports in August plunged 50% from a year ago, while shipments of steel products dropped 43.3%.
Among the biggest exporters in Japan are the carmakers Toyota, Nissan, Honda and Mitsubishi.