Mugabe's birthday was previously a major public event in Zimbabwe, marked by an outpouring of fawning congratulations and tributes in official media from regime loyalists, government ministries and agencies.
His actual birthday on Wednesday was declared an annual public holiday for the first time this year, but the occasion was greeted without fanfare.
"The party is only for close family members and friends. It is not for the public and it is strictly by invite," Louisa Nyanhongo, a member of Mugabe's close circle, told AFP.
An invitation card that appeared on social media said guests would be "celebrating our hero", alongside a smiling photograph of Mugabe.
The card said the party was at "Blue Roof" -- the lavish private residence where Mugabe and his wife Grace, 52, have been living in apparent seclusion since he was forced to resign after a military intervention.
Nyanhongo's telephone number appeared on the invitation, but she declined to comment further.
While president, Mugabe typically celebrated his birthday with a long speech while wearing a suit decorated with images of his own face at a party that included a multi-course feast.
Vast birthday cakes were a regular feature, with the biggest cake said to weigh the same number of kilogrammes as Mugabe's age. It took several men to carry it into the marquee.
Mugabe, whose 37-year rule was criticised for brutal repression of dissent and economic collapse, has not appeared in public since his abrupt ousting.
This week, he was photographed with Grace meeting the new African Union Commission chairman Moussa Faki Mahamat in Harare.
The photographs were the first of the couple since his ousting.