The official says the 86-year-old Mubarak slipped in the bathroom and broke the upper part of his thigh bone today.
The official says Mubarak will need surgery for the break. The official spoke on condition of anonymity because he was not authorised to talk to media.
Mubarak, toppled in 2011, is facing a retrial for his role in the killings of hundreds of protesters during the uprising against his rule.