After graduating from Douglass High School in Kingfisher, Oklahoma, she worked as a maid to earn enough money to attend an integrated university.

Moving to California, she worked as an editor for the Los Angeles Tribune, writing articles about racist policies such as segregation of blood supplies, immigration, and the internment of Japanese Americans during World War II.

Harris supported World Federalism as a means to maintain global peace, and attended a US–USSR summit in 1964 to promote cooperation between women.

Involved in many issues, she opposed nuclear proliferation, Cuban isolationism, intervention in Latin America, the Vietnam War, California Proposition 6, and discrimination of any kind.

As a board member of the cooperative, she helped plan the 1978 expansion of the organization to include a credit union, funeral and travel services and a public housing project.

[4][5][6] As she did not want to continue her education in a segregated setting, after graduation Harris worked as a domestic to earn enough money to attend an out-of-state integrated university.

[5][12] Harris wrote columns over the duration of World War II against Japanese-American internments, equating the government's actions as an official sanction of prejudice and warning that such discrimination could spread to other communities like Jews, Mexican Americans, and other Asians.

[4][10][13] Her articles brought her under attack by Westbrook Pegler, a fellow journalist, and to the attention of the FBI, who tapped the newspaper's phone and examined her mail.

[17] Along with other CORE members and pacifist groups she worked to assist conscientious objectors by raising funds to pay the bail bonds of resisters and publicize the issue.

[20] To keep his campaign promises and end the pressure by the Black community,[21][22] President Harry S. Truman, signed Executive Order 9981 in June 1948 to integrate the United States Armed Forces.

As soon as the decision for Brown v. Board of Education (1954) was issued by the Supreme Court, the committee began pressuring WILPF to openly support the ruling and help in enforcing school desegregation through rallies and demonstrations.

[25] Similarly, she led WILPF to adopt a policy of opposition to apartheid in South Africa, linking racial inequality to global discontent, which could lead to war.

[5][28] She was selected as a delegate for the international congress held in July in Birmingham, England, and the following month went with other women activists to attend the Commonwealth of World Citizens meeting at the Temple of Peace in Cardiff, Wales.

[36] Ultimately, the WILPF endorsed a resolution of non-violence, but recognized that violent resistance was inevitable if all other measures failed to resolve inequalities caused by the power hierarchies of a society.

[40] In March, for their community work, she and Mable Howard both received Doctor of Humane Letters degrees from the Center for Urban Black Studies, affiliated with the Graduate Theological Union of Berkeley.

[13] After her death, the City of Berkeley named the Erna P. Harris Court, a public housing project located at 1330 University Avenue, in her honor.

[1][13] An oral interview of Harris was taken in 1985 by Judith Porter Adams and is housed in the Women's International League for Peace and Freedom Collection in the Archive of Recorded Sound at Stanford University.