The University of Leicester found 83 skeletons in a Roman graveyard dating back as early as the 2nd Century.
Six with possible African ancestry is the first evidence of migrants from the continent in the city, the BBC quoted experts as saying.
Leicester is one of the UK's most diverse cities, with half its population described as white British compared to 80 per cent nationally.
Mathew Morris, project supervisor, said it showed Leicester's multiculturalism was not confined to recent decades.
More From This Section
However, the university said some bodies were buried with grave goods or exhibit burial customs not previously seen in the city.
Morris said six had African cranial features but "excitingly" two of them, one a child, appear to have been born in England.
He said by studying their teeth the team was able to tell what type of water they drank and where in the country it originated.
Through this process, known as isotope analysis, they can chart migration.
He said there are a number of theories why they were in Leicester including for trade or military reasons.
Skeletons of African origin, dating from the same period, have been found in York and at Hadrian's Wall, but this is the first evidence in Leicester.
During the excavations an elaborately decorated belt was found which would have been worn by a late Roman soldier or civil servant.
The university has been nominated for a national archaeology award for its work at the cemetery, the report said.