Delegates beat tables and whistled when African National Congress Gauteng deputy chairwoman Gwen Ramokgopa introduced Motlanthe.
Madikizela-Mandela walked in after Reverend Gift Moerane prayed for the conference. The crowd ululated and whistled as she walked in.
Other dignitaries included ANC deputy secretary general Jessie Duarte, treasurer Zweli Mkhize, and Deputy President Cyril Ramaphosa, who was expected to open the conference.
Former provincial chairs Tokyo Sexwale and Mathole Motshekga were also present.
The crowd sang “Mashatile dumela, re a go rata,” (Mashatile hello, we love you) when current ANC Gauteng chairman Paul Mashatile was introduced.
In his brief sermon, Moerane called on the ANC to lead and rule with respect.
The conference delegates will elect new provincial leaders.