He was a postdoctoral fellow with Christopher T. Walsh at MIT from 1978-1980 and continued as a faculty member at MIT from 1980-1987 whereupon he joined the faculty of the University of Michigan, Ann Arbor.

[1] In 2001, he moved to the University of California, Berkeley to assume roles as Aldo DeBenedictis Distinguished Professor of Chemistry and professor of biochemistry and molecular biology, and served as the chair of the department of chemistry from 2005 until 2010.

[3] From January 2012 to August 2014, Marletta was president and CEO of The Scripps Research Institute in La Jolla, California, succeeding Richard Lerner.

[4] Marletta is currently C. H. and Annie Li Chair in the Molecular Biology of Diseases at the University of California, Berkeley.

[5] In 2009, Marletta helped Jennifer Doudna return to UC Berkeley after working a short stint at Genentech;[6] Doudna would later win the 2020 Nobel Prize in Chemistry with Emmanuelle Charpentier for her work on CRISPR after returning to UC Berkeley from Genentech.