Germany exported €2.3 billion of goods to Russia in August 2014, a fall of 26.3 percent compared with the year before, the Federal Statistics Office (Destatis) found.
From January to August this year the value of exports to the eastern country plunged 16.6 percent on 2013 to €20.3 billion.
Some business leaders have urged Chancellor Angela Merkel to end European sanctions against Russia, which the EU introduced after Russia's annexation of Ukraine's Crimea region and its support for pro-Russian separatists in eastern Ukraine.
But Merkel said on Friday that there was no chance of sanctions on Russia being relaxed as long as a ceasefire in the east of Ukraine was not being properly observed.
Russia responded to EU sanctions by banning imports of food and drink from the EU. German food exports to Russia were worth €1.6 billion in 2013.
Before the Ukraine crisis, German exports to Russia were slipping - they were down by 5.2 percent in 2013 - but the sanctions have massively sped up the decline.
Germany's most important export to the country in the first eight months of 2014 was machinery, accounting for 22.6 percent.
Vehicles and motor vehicle parts formed 19 percent of exports, but this sector was the most heavily hit by the overall decline, with exports falling by 27.3 percent.