Starting in the early 1960s, he developed nonviolent communication, a process for supporting partnership and resolving conflict within people, relationships, and society.

He worked worldwide as a peacemaker, and in 1984 founded the Center for Nonviolent Communication, an international nonprofit organization for which he served as Director of Educational Services.

[1][2] Marshall Rosenberg's motivation for developing nonviolent communication was based on his own experiences at the Detroit race riot of 1943, as well as the antisemitism that he experienced in his early life.

His grandfather worked at Packard Motor Car Company and his grandmother taught workers' children to dance.

[2]: 752 Professor Michael Hakeem taught Rosenberg that psychology and psychiatry were dangerous, since scientific and value judgments were mixed in the fields.

Rosenberg was influenced by the 1961 books The Myth of Mental Illness by Thomas Szasz and Asylums by Erving Goffman.

Rosenberg's practicum placements were the Wisconsin Diagnostic Center, schools for delinquent girls and boys, and Mendota State Hospital.

Rosenberg started out in clinical practice in Saint Louis, Missouri, forming Psychological Associates with partners.

[7] Rosenberg went to teach his approach to conflict resolution to the group in exchange for Chappelle appearing at desegregation conventions, starting in Washington, D.C.

"I started to give my services, instead of to individual affluent clients, to people on the firing line like Al and Vicki, and others fighting in behalf of human rights of various groups."

Rosenberg decided to stay in California and promoted the Community Council for Mutual Education with the help of Vicki Legion.