"In the eyes of consumers, ongoing geopolitical tensions are now also threatening to affect the economy in Germany. And it has led to a drop in optimism," market research company GfK said in a statement.
"As a result, both income and economic expectations, as well as a propensity to spend have fallen across the board," GfK said.
Looking ahead to next month, GfK's headline household confidence index was forecast to fall to 8.3 points in October from 8.6 points in September. It also fell 0.3 points in September.
This reading is based on responses from about 2,000 households regarding their expectations about pay and the economy as a whole in the coming months, as well as their willingness to spend money.
A separate GfK index measuring economic expectations among Germans fell by six points in September, although that was a gentler drop than August, when a record 35 points were wiped off the measure.
The August recording was the steepest fall since records began 30 years ago and was blamed on worries over eastern Ukraine and Russia and conflicts in Iraq and Gaza.
Sentiment in Europe's top economy is fading as concern about the effect on investment of the crises in Ukraine and the Middle East.
Earlier this week, data showed the widely watched Ifo business climate index fell to its lowest level in 17 months in September.