This move underlined her swift political rise in the troubled southern African country.
(READ MORE: ‘Dr’ Grace Mugabe, a neophyte in the bloody ZANU PF politics)
Grace Mugabe's appointment, approved by acclamation to the resounding cheers of 12,000 delegates in a parade ground in central Harare, gives her a seat on the ruling party's top decision-making Politburo.
Over the last three months, the 49-year-old first lady has carried out a campaign against Vice President Joice Mujuru, who until recently was a leading contender in a behind-the-scenes battle to eventually succeed Zimbabwe's 90-year-old leader.
Mugabe, who has ruled the former British colony since independence in 1980, openly denounced Mujuru when he opened the congress on Thursday, accusing her of leading a group within the ruling party intent on ousting him from power.
Mugabe's comments appeared to effectively elbow out Mujuru from the race to take over from him as both ZANU-PF's and Zimbabwe's leader, leaving a seemingly clear path for her rival, Justice Minister Emmerson Mnangagwa.
(READ MORE: Zimbabwe’s Mugabe purges "treacherous" deputy once seen as successor)
The infighting within the ruling party has increased uncertainty in a country grappling with an economic meltdown which critics blame on decades of mismanagement by Mugabe.
His controversial policies, including the forcible acquisition of white-owned commercial farms for blacks, have alienated Western donors who also accuse the veteran leader of rigging elections since 2000 to stay in power.