Themba was admitted as an attorney in 1989. After graduating he was appointed State Advocate in the then Transkei, for a year and then opened his own practice in 1991. From 1997 to 2000 he also instructed candidate attorneys in High Court Practice and Criminal Court Practice at the East London School of Legal Practice. He was subsequently appointed as a judge in the Cape Division of the High Court for two terms, from October 2000 to April 2001.
In 2003 he was appointed Deputy Director of Public Prosecution in KZN, charged with establishing and running the dedicated tax prosecution unit, a position he held until joining Garlicke & Bousfield as an Executive Consultant in 2008. Themba specialises in public sector and local government law, administrative law and commercial litigation.