He participated in the Swedish Cyprus Expedition, along with archaeologists Einar Gjerstad and Erik Sjöqvist and with architect John Lindros.

Westholm carried out the excavations in: Soli, Milia, Vouni, Petra tou Limniti, Ajios Jakovos (Iron Age site), Kition, Kythrea, Amathus and Mersinaki.

[2] [6] During his stay in Cyprus, Westholm wrote many letters home which have been published in book form, and give a unique insight into the expedition's work and daily life.

In 1937 he represented Sweden at an international congress on excavation and memorial legislation, organized by the League of Nations in Cairo.

During World War II, Westholm was a secretary for a committee aimed at collecting money in support of the people of occupied Greece.

In 1956, he traveled on behalf of UNESCO to Peru to plan a new art museum in Lima.