Morale among German investors deteriorated for a third consecutive month in August, according to survey data released on Tuesday.
The ZEW research institute said its monthly survey showed its economic sentiment index fell to 10.0 from 17.5 points in the previous month. Economists had forecast a reading of 15.
A separate gauge measuring investors' assessment of the economy's current conditions ticked up to 86.7 points from 86.4 in July, compared to forecasts for 85.5.
"The significant decrease of the ZEW economic sentiment indicator reflects the high degree of nervousness over the future path of growth in Germany," said ZEW President Professor Achim Wambach.
"Both weaker than expected German exports as well as the widening scandal in the German automobile sector in particular have helped contribute to this situation. Overall, the economic outlook still remains relatively stable at a fairly high level."
The economic sentiment indicator for the eurozone fell to 29.3 points this month from 35.6 in July.
By contrast, the indicator for the current economic situation in the eurozone climbed to its highest level since January 2008, rising to 38.4 points. Since November 2016, the indicator for the economic situation in the eurozone has been steadily increasing.