Mugabe, 93, had been confined to house arrest after the military took over the country.
But today, he walked into the ceremony venue in Harare dressed in a blue academic gown and tasselled hat, before listening to speeches with his eyes closed and applauding occasionally, an AFP correspondent reported.
The generals took over late on Tuesday after vice president Emmerson Mnangagwa was abruptly sacked and Mugabe's wife Grace emerged in prime position to succeed her increasingly frail husband.
Many citizens were stunned by the military's intervention, sparked by the bitter succession battle between Grace and Mnangagwa.
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Analysts say the military leadership was strongly opposed to the rise of Mugabe's ambitious 52-year-old wife, while Mnangagwa has close ties to the defence establishment.
Mugabe and the army chiefs held talks yesterday, but no official statement has been issued on the status of negotiations that could see him eased out of office.
Government television showed Mugabe, the world's oldest head of state, at Thursday's talks standing smiling alongside army chief General Constantino Chiwenga.
But he fled to South Africa following his dismissal and published a scathing rebuke of Mugabe's leadership and Grace's presidential ambitions.
The military said today they had detained some "criminals" in Mugabe's government in a reference to supporters of Grace's presidential ambitions.
Grace has not been seen since the takeover of the military, which has not overtly called for President Mugabe's resignation.
Many Zimbabweans have either welcomed the army's intervention or were indifferent to it.
"We needed change. Our situation has been pathetic," said Keresenzia Moyo, a 65-year-old housewife in Harare.
He added that "a transitional mechanism" would be needed to ensure stability.
Tendai Biti, who served as finance minister during the coalition government after the 2008 elections, called it "a very delicate time for Zimbabwe".
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