He served as assistant director for history and culture research and directed the Office for Latin America, at the Smithsonian National Museum of the American Indian from 2006 to 2017.
In 1994, on the occasion of the opening of the Heye Center in New York, he worked with the museum to produce Native American Expressive Culture as a special edition of the Akwe:kon Journal.
In Central and South America, Barreiro presently advises and advocates for indigenous or originario communities in Cuba (guajiro-taino), Guatemala (Maya-Q'eqchi') and Peru (Quechua – high mountain).
In Cuba and the Caribbean, his current work sustains an increasingly accepted twenty-year campaign for the recognition for his own indigenous people (eastern plains and mountains), after centuries of marginalization and quasi-legal, historical dictums of extinction.
In North America, Barreiro is involved in the application of principles of indigeneity in Native community education and socialization, particularly around the work of healing and strengthening of young people and families.
Barreiro: "The emergence of a heartfelt mandate toward family healing processes in Native North American communities is an increasingly detectable movement that couples traditional principles of practice and the most current medical research in the search in developing new approaches and structures for the health of humans and the natural world."
Barreiro married Katsi Cook, a Mohawk midwife, environmentalist, Native American rights activist, and women's health advocate in the early 1970s.