Educated at Jan van Riebeeck Secondary School, Cape Town and at the University of Cape Town.
He began working as a telegraphist at the Post Office and then moved to its translation bureau. Next he turned to journalism as a reporter on “Die Transvaler" in 1937. He made his mark and was promoted to manager of Die Transvaler Boekhandcl in 1940 at Potchefstroom and afterwards at Pretoria.
His apprenticeship for his political career began as one of the founders of the Nasionale Jeugbond. He was provincial leader in Pretoria from 1940 to 1945. He became National Party organiser at Natal in 1943 and was later transferred to Transvaal. In March 1949 he was elected to the Provincial Council as member for Pretoria Central. Two years later he was appointed National Party information officer in the Transvaal.
After being elected MP for Alberton in 1953 Viljoen was an active backbencher until he was appointed Deputy Minister of Lands and Mines on December 1, 1958. It took him eight years to reach cabinet rank. In 1966 he became Minister of Labour and Minister of Coloured Affairs. In the reconstitu¬ted cabinet after the elections in April 1970 he became Minister of Interior and Minister of Labour. A further reshuffle within a year gave him the portfolios of Labour, Posts and Telegraphs.
In February 1971 he faced protests from white unions for exempting the building industry from job reservation. He resisted them vigorously on the grounds that the chronic shortage of skilled men required him to make it possible for Coloureds to take jobs as bricklayers.
Transvaal Province Council for Pretoria 1949-1953.
Respected for being less dogmatic than many of his cabinet colleagues, he could go much further as a politician acceptable to both wings of the National Party. Despite white trade union pressures, Viljoen is not a man to be rushed into applying job reservation measures, as a form of economic segregation, when they are likely to exacerbate the labour shortage problem. An interesting “late-developer” closely watched by political pundits.
He was married on 20 April 1940 to Dorothea Maria Brink (17 September 1917 – 5 October 2005), with whom he had one daughter Elizabeth Magdalena (Elna) Viljoen.