German citizens cited Mr Trump’s decision to pull out of the Iran nuclear deal and Paris climate accord - along with his hostility towards Germany - as the main reasons for ranking him their biggest single worry.
The “Fears of Germans” survey showed 69 percent of respondents view the US president as their top concern. The poll is published every year by the R+V Versicherung insurance company.
Immigration was the second-biggest concern, named by 63 percent of people, closely followed by the social tensions a large influx of newcomers has created.
The next major worry was doubt about politicians’ ability to handle complex problems. Terrorism, last year’s biggest fear, was ranked in fifth place.
“More than two-thirds of Germans have a great fear that the politics of Donald Trump are making the world a more dangerous place,” said survey institute director Brigitte Roemstedt.
Mr Trump has repeatedly criticised Chancellor Angela Merkel and the German government this year. In June he claimed the people of Germany were “turning against their leadership” over migration, and also attacked the country’s defence spending and export policy.
And in July he accused Germany of being “totally controlled” by Russia over a proposed natural gas deal.
“Trump’s ruthless America First policy, his aggressive stance against international agreements and his no less aggressive stance on trade and security, including against allies, is scaring a majority of the population,” said political scientist Manfred Schmidt.
“This is reinforced by Trump’s attacks against Germany,” he added.
“If the US should refuse to provide military assistance to countries with supposedly low defence expenditures, this would put Germany in a difficult position, given its current inability to defend itself.”
Eurozone debt problems, political and religious extremism, natural disaster linked to climate change, environmental problems and the country’s ageing population were all ranked in the top 10 fears faced by Germans today.