Theuns served as minister of religion in Pretoria from 1983 to 1989. He completed his Doctorate in theological ethics. Theuns left the ministry in 1989 and joined the Consultative Business Movement (CBM). He headed the administration of Codesa and was Deputy Director of the Transitional Executive Council before the 1994 elections. From 1995 he is the CEO of the National Business Initiative. He became Vice-Chancellor of Potchefstroom University for CHE in 2002 and headed the merged North West University (NWU) from 2004. He completed his second term at the NWU in May 2014. Theuns acted as CEO of the FW de Klerk Foundation until 31 May 2019.