He was mayor of Stokken, MP from 1925 to 1930, Minister of Education and Church Affairs from 1935 to 1945 and County Governor of Aust-Agder from 1945 to 1961.

He was born at Hopland in Alversund municipality as a son of farmer Nils Hjelmtveit, Sr. (1861–1911) and his wife Ingebjørg Herland (1865–1893).

In 1935, when Nygaardsvold's Cabinet assumed office, Hjelmtveit was appointed Minister of Education and Church Affairs.

[1] Some of the cases that were decided during Hjelmtveit's tenure were naming of the committees that prepared the University of Bergen, Riksteatret and the Norwegian State Educational Loan Fund, closing of the teachers' colleges at Hamar and Notodden, the language reform of 1938, poet's grant to Arnulf Øverland, construction of Kringkastingshuset and the signing of a Norwegian-Czechoslovak cultural cooperation treaty.

[1] Between the war's end (8 May 1945) and Hjelmtveit's return to Norway, Alv Harald Helland and Terje Wold filled in as Minister of Education and Research.