China's exports last month decreased 3.2 per cent from a year earlier, following August's 1-per cent drop, Efe news reported citing the General Administration of Customs (GAC) data.
A Wall Street Journal (WSJ) poll of economists had tipped a 3 per cent decline.
Imports slid 8.5 per cent on year in September, extending August's 5.6 per cent drop, the customs data showed.
The WSJ poll had forecast a decline of 6 per cent.
China's overall trade surplus stood at $39.65 billion in September, wider than August's $34.8 billion surplus and the $34.05 billion surplus that had been expected.
According to the GAC, the total trade volume for the first three quarters of 2019 grew 2.8 per cent year-on-year, reaching 22.91 trillion yuan ($3.2 trillion).
Exports grew by 5.2 per cent in the same nine-month period compared to the previous year, while imports shrank 0.1 per cent.
Between January and September this year, China's trade surplus was 2.05 trillion yuan ($290 billion), an increase of 44.2 per cent compared to the first three quarters of 2018.
Trade tensions between China and the US have eased a little following last week's high-level trade talks, with Washington shelving new tariffs against Beijing while leaving many demands to be worked out later, in return for an assurance of increased agriculture purchases by China.
( With inputs from IANS )