During his tenure at IPAC, Jarrett has performed hardware instrumentation, software engineering, and scientific research across a wide range of fields in astronomy. He assisted in developing a near-infrared camera system for the Hale 200" Telescope of the Palomar Observatory, conducting research on young stellar objects, star formation regions and nearby galaxies.

In 1994 Two-micron All Sky Survey (2MASS) and was charged with detecting, characterizing and cataloging extended sources. Using the 2MASS 'galaxy' catalogs, Jarrett has conducted research in the large scale structure that comprises the local universe. In 2003, he then joined the Spitzer Legacy teams "SINGS" and "SWIRE", focusing his research on star formation in low-redshift galaxies. Participating in and/or leading a number of Spitzer GO projects, Jarrett has studied interacting galaxies (notably the "Tadpole Galaxy"), clusters and large scale structure (notably the "Great Attractor"), and the most massive HI galaxy in the local universe (aka "The Coelacanth Galaxy").