[3] Mthembu served as the MEC for Transport in Mpumalanga from 1997 to 1999, during which he was criticized for spending R2.3 million on ten BMWs.
[4][5] Mthembu was elected to National Assembly of South Africa in 2014 where he served till his death in 2021.
On 28 November 2017, some of Mthembu's ANC colleagues criticised him for "colluding" with the DA to schedule a debate on state capture in Parliament in defiance of President Jacob Zuma and his colleagues in the ANC caucus who had already called for a more inclusive process to investigate state capture.
His daughter, 25-year-old Nokhwezi Mthembu, committed suicide on 20 March 2019, at their Pelican Park parliamentary village home in Cape Town.
The armed man and his accomplices proceeded to Mthembu's car, where four of his friends were waiting for him, and robbed them of their money and cellphones.