Johannes de Klerk was born on 22 July 1903 in Burgersdorp. He was the eldest son of Reverend Willem de Klerk and Aletta Johannes van Rooy. De Klerk went to school at Potchefstroom and from 1923 to 1926 studied at the Potchefstroom University College for Christian Higher Education where he obtained a BA degree and Higher Education Diploma. He was actively involved in student politics. From 1925 to 1926 De Klerk was chairman of the Students’ Representative Council. On 11 April 1927 he married Hendrina Cornelia, with whom they had two sons Willem Johannes and Frederick Willem.
Between 1927 to 1945 he taught at Nylstroom and on the Witwatersrand and was subsequently appointed headmaster of the Afrikaans-medium school at Primose East. He was later appointed secretary to the White Workers’ Protection Union aimed at fighting communism in workers’ circles on the Rand. He was appointment in January 1947 as the Organising secretary of the National Party on the Rand. In August 1948 he was made Chief Secretary of the NP in the Transvaal, and delivered on his mandate of providing a successful campaign for the party in the provincial election of 1949.
In 1954 De Klerk was appointed Minister of Labour and Public Works and objections were raised over his sudden rose in ranks since was appointed by his brother–in–law, advocate J.G.strijdom. The very same year he was appointed Senator. Over the years he held the following portfolios in parliament: Labour and public Works (1954 – 58), Labour and Mining (1958 – 61), Internal Affairs, Labour and Immigration (1961), Internal Affairs and Education, Arts and Science (1961 – 66), Education, Arts and Science and Information (1966 – 67), and National Education (1967 – 68).
De Klerk was instrumental in the founding of the Rand Afrikaans University (RAU) and University of Port Elizabeth (UPE). For many years he was chancellor at the Potchefstroom University for Christian Higher Education. The University of Potchefstroom and University of Port Elizabeth honoured him with doctorates for his contribution to education. In 1967 he was widely tipped to be President of South Africa and it never happened. The following year he was approached to stand as a candidate and turned the offer down in support of J.J. Fouche. In June 1969 he appointed President of the Senate.
In 1976 he resigned as President of the Senate and spent his last years on a farm in Krugersdorp, where he died on 24 January 1979. A school in Krugersdorp has been named after him for his contribution in education in that part of the country.