After graduating with a PhD at Cornell, he briefly taught at Brooklyn College before accepting a position at University of California, Davis, where he stayed for thirty-seven years.

[1] While finishing his PhD, Starr returned to Brooklyn College as an assistant professor of biology.

[8] In 1949, he spent three months in Colombia to help identify a plant pathogen that was killing pasture crops used by dairy farmers.

[10] In 1973, he succeeded Charles E. Clifton as the editor of the academic journal the Annual Review of Microbiology.

[11][12] Starr was the editor of several books, including The Prokaryotes: a handbook on habitats, isolation, and identification of bacteria (1981).