"A majority (55 per cent) says they have been subjected to racial slurs or jokes, and about one-in-four (24 per cent) have felt annoyed because people have made assumptions about their racial background," said Pew Research Centre report.
At the same time, majorities of multi-racial adults are proud of their mixed racial background (60 per cent) and feel their racial heritage has made them more open to other cultures (59 per cent), said the report.
By comparison, 2.1 per cent of adult Americans said they were two or more races in the Census Bureau's 2013 American Community Survey.
According to the report, not all adults (61 per cent) with a mixed racial background consider themselves "multi-racial."
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About a third (34 per cent) say they never knew the family member or ancestor who was of a different race.
Three-in-ten adults with a multi-racial background say that they have changed the way they describe their race over the years - with some saying they once thought of themselves as only one race and now think of themselves as more than one race, and others saying just the opposite.
Multiracial Americans are younger than the country as a whole. Today, nearly half (46 per cent) of all multiracial Americans are younger than 18, according to census data.
Pew said mixed-race couples and births of children who have a multiracial background have increased.
Since 1980, the share of marriages between spouses of different races has increased almost fourfold -- from 1.6 per cent to 6.3 per cent in 2013.
The share of multiracial children is growing at an even faster rate.
In 1970, among babies living with two parents, only one per cent had parents who were different races from each other.
By 2013, that share had risen to 10 per cent.