He was most noted for his research of the ancient Mediterranean, particularly known for his work on Cyprus,[1] as well as his studies of early Rome.

In 1922 he was an assistant at excavations in Asine under Axel W. Persson (1888–1951), professor of classical archaeology and ancient history at Uppsala University.

The expedition was intended to make a complete study of the ancient culture of Cyprus.

Gjerstad served as the expedition's leader with overall responsibility, while Erik Sjöqvist and Alfred Westholm led most of the excavations.

When Gjerstad left Rome in 1940, he assumed the position of Professor of Classical Archaeology and Ancient History at Lund University.