Apart from his 54 uninterrupted years of teaching Economics until 2011, Terreblanche is also known for his involvement in party politics, including clandestine meetings with the ANC toward the end of the 1980s. In 1985, he was appointed Chairman of the newly formed Discussion Group ’85 at the University of Stellenbosch (US).

Terreblanche ended his membership with the National Party in 1987 and became one of its strongest critics. He was a founding member of the Democratic Party and its first economic adviser.
 

Terreblanche began his academic career as a student at Stellenbosch from 1951 to 1956, where he attained a bachelor’s degree in law in 1954 and a master’s degree in economics (cum laude) in 1957. He lectured in Economics at the former University of the Orange Free State in 1957 at the age of 23 and was promoted to Senior Lector in 1960.

He obtained his DPhil in Economics in March 1963. In his thesis, The history of economic thought, he presented a critical analysis of the economic writings of eight prominent economists. His plea for a social democratic rather than a laissez-faire approach to economic policy was born from his conclusions in his thesis. During 1968/69 he attended Harvard University, where he audited a number of courses and worked with leading scholars, mainly specialists in economic history and the history of economic thought.

Terreblanche was a lecturer and professor in Economics at Stellenbosch University from 1965 until his retirement in 1995. He went on to become an emeritus professor. He continued lecturing until the end of 2011, concluding a career of uninterrupted teaching in Economics that spanned 54 years.

Prof Terreblanche has published 11 books and more than 30 articles in journals and chapters in books. He is a prolific writer of newspaper articles, mainly on political and economic issues concerning South Africa's long transitional period from 1980 onwards. He regards Politieke ekonomie en sosiale welvaart (1986) and A history of inequality in South Africa: 1962–2002 (2002) as his most important works. In 2012 he updated the final chapter of his book Lost in transformation: South Africa’s search for a new future since 1986.

He was a member of the board of the SABC from 1972 to 1987 and their Vice-Chairman from 1982 to 1987. He was a member of the Commission of Inquiry Relating to Matters Concerning the Coloured Population Group (the Erica Theron Commission) from 1973 to 1976. He served on the Economic Advisory Board of the Prime Minister (later State President) between 1979 and 1985.

In 1992, he received the Stals Award for Economics from the South African Academy for Science and Arts.