The mood among German consumers worsened more than expected heading into March to reach its lowest level in four months.
A new survey cited rising inflation and economic risks linked to the policies of US President Donald Trump for the decline.
The consumer sentiment indicator, published by the Nuremberg-based GfK institute and based on a survey of around 2,000 Germans, fell to 10 going into March.
A Reuters poll had expected a fall to 10.1 from 10.2 a month earlier.
GfK's index contrasts with this week's Ifo index that showed German business morale rose in February, and with bullish overnight comments from the German finance ministry.
Compiler GfK said all three component of its index - overall economic expectation, personal income expectation and propensity to buy - fell after three increases in a row.
"The policies of the new U.S. president are causing uncertainty and economic worry among German consumers," GfK said.
"Donald Trump's plans to bolster protectionism are giving rise to job insecurity primarily among workers in industries that rely heavily on exports, such as the automotive and machine engineering, as well as the chemical industry," it added.
GfK said the subindex measuring consumers' expectations for the economy fell, but it still remained on a fairly high level, lying six points above the previous year's reading.
The decline in personal income expectations was put down to rising consumer prices after German inflation picked up to 1.9% in January.
The German economy grew by 1.9% in 2016, the strongest rate in five years, driven by private consumption, state spending and construction.
For this year, the German government forecasts a weaker growth rate of 1.4% because there will be fewer workdays and exports are likely to rise less strongly than imports.
Germany's solid labour market, coupled with increased state spending and low interest rates, has boosted consumption. This trend is expected to continue this year, however at a slightly slower pace.
The GfK subindex measuring the prospensity to buy fell to 51.6, slightly lower than the corresponding period of last year.
