Dash grew up in New York City and later attended Howard University. He spent 1969-1970 as a Peace Corps high school teacher in Kenya. He joined the Washington Post in 1965 where he worked as a member of the special projects unit, as part of the investigative desk, and as the West Africa Bureau Chief.

Rosa Lee, which started as an eight-part series for the Washington Post in September 1994, is the story of one woman and her family's struggle against poverty in the projects of Washington D.C.

Aside from winning a Pulitzer Prize for Explanatory Journalism for the story, The Rosa Lee piece was also the recipient of the Robert F. Kennedy Journalism Award and later published into a book. It was picked as one of the best 100 pieces in 20th-century American Journalism by New York University's journalism department.

While living in the inner city of Washington, D.C. for a year, Dash researched teenage pregnancy in black youths for his book, When Children Want Children: The Urban Crisis of Teenage Childbearing. The book features conversations with teens and contains stories that contradict the common belief that inadequate birth control and lack of sex education classes are the causes of teenage pregnancy.

He received an Emmy Award in 1996 from the National Academy of Television Arts and Sciences for a documentary series in the public affairs category of hard issues.

In 1998 Dash joined the University of Illinois as a professor of Journalism. He was later named the Swanlund Chair Professor of Journalism, Law, and Afro-American Studies in 2000. Three years later he was made a permanent faculty member in the University's Center for Advanced Study.