The extravagant celebrations were held against a backdrop of economic ruin and came weeks after the veteran leader joined a unity government with long-time rival Morgan Tsvangirai.
"I am still in control and hold executive authority, so nothing much has changed," Mugabe told a crowd of about 2 000.
"Under this arrangement I want it known, as some of you were thinking we are no longer in power, we have an inclusive government with the president at the top, followed by the two vice-presidents, then the Prime Minister Tsvangirai and two deputy prime ministers.
"This is a result of the vote in which we did not do well. Let us not complain too much about it. Let’s accept things as they are."
‘Some sold Zimbabwe out’
The veteran president, who has ruled Zimbabwe non-stop since independence in 1980, blamed former colonial power Britain for his party’s defeat at the polls and accused those who turned against Zanu-PF of being traitors.
"They (British) imposed sanctions which resulted in some basic commodities being unavailable so that the people would be disgruntled with the party.
"Some of you thought about your tummies and children and sold out the country," he blasted.
Mugabe supporters raised more than US$250 000 for Saturday’s celebrations which included a birthday cake weighing 85 kilograms.
The party was held north of the capital Harare in the town of Chinhoyi in Mugabe’s home province of Mashonaland West.
‘Mugabe never lets his people down’
Crowds arrived in lorries, singing songs in praise of Mugabe, while banners proclaimed him a "great leader who never lets his people down".
Tsvangirai, who has been rallying the donor community for $5bn in aid and investment, was not at the celebrations despite initial reports he would attend.
The country desperately needs money to rebuild schools, hospitals and sewers after a decade of economic collapse compounded by country’s long political travails.
Chinhoyi local Leo Matiyashe, who runs a food kiosk in the town, had to put business above pleasure as crowds flock to the party.
"I am in business looking for money and I cannot afford to close my shop to attend the birthday party."
Several members of Mugabe’s Zanu-PF have farms in Mashonaland West and conditions are considerably better than the rest of the shattered country with a university and one of the best-equipped state hospitals.