Japan's current account surplus fell 21.4 percent in September from a year earlier to 1,584.8 billion yen (20.4 billion U.S. dollars), the Ministry of Finance said in a preliminary report on Wednesday.
The surplus narrowed less than median forecasts for a 31.3 percent decline in the recording period and September's fall marked the seventh consecutive month of decline, the ministry's data showed.
The balance of trade in goods registered a surplus of 373.2 billion yen, compared to a deficit of 694.7 billion yen booked in the previous month, the data also showed.
In addition, the MOF said that Japan's current account surplus declined 46 percent in the first half of fiscal year 2011, standing at 4.52 trillion yen.
Japan's current account balance is one of two major gauges of its foreign trade and a current account surplus increases the nation's net foreign assets.
The balance of trade is the difference between a country's exports of goods and services and its imports.