In 1930 Erikson married Joan Mowat Serson, a Canadian dancer and artist whom Erikson had met at a dress ball. During their marriage Erikson converted to Christianity.
In 1933, with Hitler's rise to power in Germany, the burning of Freud's books in Berlin and the potential Nazi threat to Austria, the Eriksons left an impoverished Vienna with their two young sons and emigrated to Copenhagen. Unable to regain Danish citizenship because of residence requirements, the Eriksons left for the United States, where citizenship would not be an issue.
In the U.S., Erikson became the first child psychoanalyst in Boston and held positions at Massachusetts General Hospital, the Judge Baker Guidance Center, and at Harvard Medical School and Psychological Clinic, establishing a singular reputation as a clinician.
In 1936, Erikson left Harvard and joined the staff at Yale University, where he worked at the Institute of Human Relations and taught at the Medical School. While at Yale he became a naturalized citizen of the United States and changed his family's surname from his adoptive father's name of "Homburger" to "Erikson."
Erikson continued to deepen his interest in areas beyond psychoanalysis and to explore connections between psychology and anthropology. He made important contacts with anthropologists such as Margaret Mead, Gregory Bateson and Ruth Benedict, and these contacts, in turn, led to an excursion in 1938, which was to prove significant in the development of his thinking; he was invited to observe the education of native Sioux children on the Pine Ridge Indian Reservation in South Dakota.
In 1939 he left Yale, and the Eriksons moved to California, where Erik had been invited to join a team engaged in a longitudinal study of child development for the University of California at Berkeley's Institute of Child Welfare. In addition, in San Francisco he opened a private practice in child psychoanalysis.
While in California he was able to make his second study of Native American children when he joined anthropologist Alfred Kroeber on a field trip to Northern California to study the Yurok.
In 1950, after publishing the book, Childhood and Society, for which he is best known, Erikson left the University of California when California's Levering Act required professors there to sign loyalty oaths. From 1951 to 1960 he worked and taught at the Austen Riggs Center, a prominent psychiatric treatment facility in Stockbridge, Massachusetts, where he worked with emotionally troubled young people. During this time he also served as a visiting professor at the University of Pittsburgh where he worked with Benjamin Spock and Fred Rogers at Arsenal Nursery School of the Western Psychiatric Institute.
He returned to Harvard in the 1960s as a professor of human development and remained there until his retirement in 1970. In 1973 the National Endowment for the Humanities selected Erikson for the Jefferson Lecture, the United States' highest honor for achievement in the humanities. Erikson's lecture was titled "Dimensions of a New Identity".