She worked as a psychologist, professor, and health occupation specialist before serving as a member of the Los Angeles Unified School Board (1975–78).

When, in 1988, the US government proposed the addition of the category of "bi-racial" or "multiracial" to official documents and statistics, some African American organizations and African American leaders such as Watson and Representative Augustus Hawkins were particularly vocal in their rejection of and opposition to the category.

After a hard-fought campaign that often turned negative, Watson narrowly lost to former Supervisor Yvonne Burke, who was supported by U.S. Representative Maxine Waters.

[citation needed] In 1999, President Bill Clinton appointed her United States Ambassador to Micronesia and she served in the post for two years.

She stepped down to run in the April 2001 Democratic primary election, which was called to nominate a candidate to replace Congressman Julian Dixon, who had died in office five months earlier.

[1] In Congress, she became a vocal leader on issues related to racism and xenophobia, supporting reparations for descendants of American slaves, reform of the educational system, subsidies for families lacking health care, and a comprehensive overhaul of the nation’s criminal justice system.

She also decried incidents of violence and racism against Arab Americans that she believed were a result of retribution for the September 11, 2001, terrorist attacks.

She opposed the Cherokee Nation's March 2007 vote to amend its constitution to limit citizenship to only those descendants with at least one Indian ancestor on the Dawes Roll.

[1] In the 2008 Democratic primary, Watson's district went overwhelmingly for Illinois Senator Barack Obama by a margin of 61-29.