About 282,913 cars were registered last month, a drop of 4.7 percent compared to sales in the same month in 2012, according to the official KBA agency.
Over the first six months of the year combined, 1.503 million cars were registered, 8.1 percent fewer than in the same period a year earlier, the agency said in a statement.
The European car industry overall has been hard hit by first the financial crisis and then by the effects of the eurozone debt crisis.
However, top German manufacturers have resisted better than many other carmakers in Europe, particularly with the export of high-quality cars.