Galarza worked as a labor organizer and a key leader in laying the groundwork for the emergence in California of the farm labor movement. National Farm Labor Union. Galarza begin organizing farm workers in California in 1948 as research and education director of the American Federation of Labor's short-lived National Farm Labor Union.
Galarza organized a 1947 strike against the DiGiorgio Corporation in Arvin, California that lasted 30 months, and entangled the company and the union in suits and counter-suits for the following 15 years. Altogether between 1948 and 1959, Galarza and the union initiated some twenty strikes and labor actions.
Although primarily an intellectual and scholar whose weapons were words, Galarza initially played an activist's role with the AFL as the leader of several strikes. But he was completely thwarted by the bracero program and so abandoned the union leader's weapon of direct economic action for the intellectual's weapon of words in hopes of killing the program.
A prolific writer, Galarza's best-known work is Merchants of Labor (1964), an exposé of the abuses within the Bracero Program. The book was instrumental in the ending of the program, which in turn opened the door for Cesar Chavez to begin unionizing immigrant farmworkers in 1965.
In 1956 Galarza was awarded the Bolivian Order of the Condor of the Andes. The Ernesto Galarza Applied Research Center at the University of California Riverside, and other California elementary and secondary schools, bear his name. His many books include:
- Barrio Boy, 1971
- Merchants of Labor: The Mexican Bracero Story, 1964
- Spiders in the House and Workers in the Field, 1970