After a stint at the Royal Gun Factory, in 1919 he received a Columbia University fellowship to study radio engineering under John H. Morecroft.
In 1920 Friis joined a Western Electric Company research group which in 1925 became part of Bell Laboratories.
During World War II, Friis invented a "rocking horse" mechanical scanner for radar used to locate enemy mortars.
In 1958 he retired but continued as a research consultant to the Hewlett-Packard Company as a friend of David Packard.
Friis died on 15 June 1976, at age 83, of a stroke in Palo Alto, California.