Research in physics at the University of Trieste began officially on July 2nd, 1945, with the birth of the "Istituto di Fisica", later reorganized as the "Dipartimento di Fisica" (Physics Department) on October 18th, 1984, and located in Via Valerio, 2. By an agreement with the  "Istituto Nazionale di Fisica Nucleare" (INFN - the Italian National Institute for Nuclear Physics), the same university building hosts some of the offices and laboratories of the INFN (Trieste Section).

The Department of Theoretical Physics, originating from the previous "Istituto di Fisica Teorica", dates back to January 1st, 1985. Like the previous Institute, it was located at the Miramare site, a University property hosting the Unesco International Centre for Theoretical Physics (ICTP).

Research in astronomy in Trieste dates back to the foundation of an Observatory in 1850, when Trieste was part of the Austrian Empire. The Astronomy Department, originating on January 24, 1985 from the "Istituto di Astronomia", was located at the "Osservatorio Astronomico Triestino" (OAT), which is now part of the "Istituto Nazionale di Astrofisica" (INAF - National Institute for Astrophysics).

On October 1st, 2009, the three university Departments, already having close links both as regards research and teaching activities, joined together to form the new Department of Physics.