Bellah received a BA from Harvard University in 1950, and a PhD from Harvard in 1955. He was a student of Talcott Parsons, sociologist at Harvard and he and Parsons remained intellectual friends until Parsons' death in 1979. Parsons was specially interested in Bellah's concept of religious evolution and the concept of "Civil Religion." While an undergraduate at Harvard, he was a member of the Communist Party USA in 1947–1949 and a chairman of the John Reed Club, "a recognized student organization concerned with the study of Marxism". During the summer of 1954, Dean of the Faculty of Arts and Sciences at Harvard McGeorge Bundy, who later served as a national security adviser to John F. Kennedy and Lyndon B. Johnson, threatened to withdraw Bellah's graduate student fellowship if he did not provide the names of his former club associates. Bellah was also interrogated by the Boston office of the FBI with the same purpose. As a result, Bellah and his family spent two years in Canada, where he was awarded a post-doctoral fellowship at the Islamic Institute in McGill University in Montreal. He returned to Harvard after McCarthyism declined due to the death of its main instigator senatorJoseph McCarthy. Bellah afterwards wrote,
...I know from personal experience that Harvard did some terribly wrong things during the McCarthy period and that those things have never been publicly acknowledged. At its worst it came close to psychological terror against almost defenseless individuals. ...The university and the secret police were in collusion to suppress political dissent and even to persecute dissenters who had changed their minds if they were not willing to become part of the persecution.
—Robert N. Bellah
Bellah's magnum opus, Religion in Human Evolution (2011), traces the biological and cultural origins of religion and the interplay between the two. Philosopher Jürgen Habermas wrote of the work: "This great book is the intellectual harvest of the rich academic life of a leading social theorist who has assimilated a vast range of biological, anthropological, and historical literature in the pursuit of a breathtaking project... In this field I do not know of an equally ambitious and comprehensive study."
Bellah is also known for his 1985 book Habits of the Heart, which discusses how religion contributes to and detracts from America's common good, and for his studies of religious and moral issues and their connection to society. Bellah was perhaps best known for his work related to American civil religion, a term which he coined in a 1967 article that has since gained widespread attention among scholars.
He served in various positions at Harvard from 1955 to 1967 when he took the position of Ford Professor of Sociology at theUniversity of California at Berkeley. He spent the remainder of his career at Berkeley. His political views are often classified ascommunitarian. An academic biography of Robert Bellah, "the world's most widely read sociologist of religion", is currently under way.