The province decided at its nomination conference on Thursday night to back Motlanthe over the incumbent, President Jacob Zuma.
Other branches around the country, as well as the ANC Youth League, have decided to nominate Motlanthe.
He, however has not yet indicated whether he will accept the nominations.
The province chose to retain Gwede Mantashe as secretary general.
Tokyo Sexwale was nominated for deputy president, Febe Potgieter for deputy secretary general, North West premier Thandi Modise for chairwoman, and Gauteng ANC chairman Paul Mashatile for treasurer.
The Gauteng ANC said 432 delegates were expected to attend the conference. However, only 412 were present on Thursday night.
“The provincial nominations conference represented the democratic views and wishes of the overwhelming majority of the members of the ANC in Gauteng,” it said.
“We are satisfied that the outcome of the results... will push for [the] renewal of the organisation.”
It said the conference had consensus on the selection of 80 national executive committee members.
“The results will place our province in a position to forge ahead with speed in implementing the ANC’s priorities which are informed by the plight of our society.”
At the sidelines of the conference on Thursday night Mashatile said delegates were allowed to debate on their choice of candidates without fear of intimidation.
“We have agreed as Gauteng that let’s allow branches to discuss their will freely, and... today [Thursday] there is nobody fighting here,” he told reporters on the sidelines of the conference.
“Once the process of voting is done, we will accept that those are the results, and those names will go forward as the nomination of Gauteng.”
The provincial conference consolidates branch nominations ahead of the African National Congress’s national conference in Mangaung in December.
Before the conference began, members from the Ekurhuleni region sang about former ANC president Oliver Tambo, and held up two fingers, symbolising a second term for Zuma.
They later sang in favour of “Msholozi” — Zuma’s clan name.
The Gauteng provincial executive committee had previously decided to ban t-shirts with slogans or images supporting candidates, or songs that derided them.
A few female delegates cheered after Mashatile entered the venue in Turffontien. They then rolled their hands in a motion associated with calling for the substitution of a soccer player.
This gesture is linked to the call for Motlanthe to replace Zuma in Mangaung.
When Mashatile introduced himself to delegates, all cheered, except those from Ekurhuleni. Several rolled their hands.
“I am happy when you are singing and not insulting anyone,” Mashatile said.