Cambridge University produces the most employable graduates in the UK, according to a new poll.
The prestigious institution scored a top 10 place in new international rankings, making it the highest placed UK university.
In total, four UK institutions made it into the top 30 of the seventh annual Global University Employability rankings.
But each has slipped down the table slightly, and one expert said questions are likely to be asked about whether Brexit is "tarnishing the image" of UK universities.
The falls come amid a rise in Asian universities, as well as other factors such as English usage becoming more widespread, it was suggested.
The rankings are based on data gathered by HR consultancy Emerging from around 6,000 recruitment managers at large international firms, who were asked what they look for in graduates and to vote for the institutions they believed produce the most employable graduates.
Cambridge took fifth place in the latest table, published by Times Higher Education, compared with fourth last year.
Topping this year's rankings was the California Institute of Technology, followed by Harvard University, Columbia University and then the Massachusetts Institute of Technology - all in the United States.
The other UK institutions making it into the top 30 were Oxford in 15th place (seventh last year), Imperial College London in 17th place (16th), and King's College London in 25th place (23rd).
Simon Baker, data editor at Times Higher Education said: "UK universities have taken a severe knock in the Global University Employability Ranking and questions will be raised about whether the Brexit process is tarnishing the image of its universities in the eyes of global recruiters.
"However, the UK's general decline in the ranking has been happening for some time, a product of the rise of Asian universities, the use of English becoming widespread - therefore removing the UK's natural competitive advantage - and a traditional weakness in UK institutions' industry links.
"The odds on the UK turning this situation around in the short term appear slim and it underscores the need to avoid Brexit leaving the country isolated on the world stage."
Sarah Stevens, of the Russell Group, which represents 24 leading universities, said: "We know employers value the skills that Russell Group graduates develop through an education informed by the latest cutting-edge research.
"Eighty per cent of Russell Group graduates are in professional employment six months after leaving university and they are likely to receive a higher average salary too.
"Our members are investing significant resources into careers and employment support to ensure students leave higher education ready to thrive in the workforce."