"Not only have they made the world better, but by following their example they make us a little bit better every single day. We are truly grateful to them," the president said in a White House ceremony.
The group included Ethel Kennedy, widow of the late Senator Robert Kennedy; NBC journalist Tom Brokaw; and Representative John Dingell, a Michigan Democrat and the longest-serving member of Congress. Dingell is retiring at the end of the year.
Others recognized at the ceremony were author Isabel Allende, Native American activist Suzan Harjo and former U.S. Representative and federal judge Abner Mikva of Illinois.
Also receiving awards were actress and humanitarian Marlo Thomas, Nobel Prize-winning economist Robert Solow, pioneering black golfer Charles Sifford and physicist Mildred Dresselhaus.
Posthumous medals were awarded to six people, among them civil rights workers James Chaney, Andrew Goodman and Michael Schwerner. They were killed in 1964 as they participated in a voter registration drive in Mississippi.
Other posthumous awards went to choreographer Alvin Ailey and to Representatives Patsy Mink of Hawaii, a sponsor of Title IX legislation banning sexual discrimination in higher education, and Edward Roybal of California, founder of the Congressional Hispanic Caucus.
Obama said composer Stephen Sondheim was to have received the medal but could not attend the ceremony. He will receive it next year, he said.
The Presidential Medal of Freedom is reserved for individuals who have made "meritorious contributions" to U.S. security, world peace or cultural endeavors.