Realizing that public sector organizing was what she enjoyed most, Chavez-Thompson joined the staff of the American Federation of State, County and Municipal Employees as an International Representative in 1971. She then went to work for (AFSCME Local #2399) in San Antonio in 1973 as an assistant business agent. She was promoted to business agent, then was appointed executive director of Local 2399, AFSCME's San Antonio affiliate. She became a fixture on local TV and in local newspapers. In 1978, she opposed a wildcat strike by members of her local, knowing they would be fired for striking.