Islamist militants have set off bombs in Cairo since the 2013 overthrow of president Mohamed Morsi.
The blast in the Maadi district, caused by a "strange metal device", killed a 35-year-old doorman as he cleaned a garden, the ministry said in a statement.
His wife and two sons were injured in the explosion.
Islamist militants have set off bombs in Cairo, usually targeting policemen, since the 2013 overthrow of president Mohamed Morsi, a Muslim Brotherhood politician.
His overthrow led to a deadly police crackdown that killed hundreds of Islamist protesters, and an insurgency centred in the Sinai Peninsula that killed hundreds of soldiers and policemen.
Maadi is a large district that houses embassies and expatriates as well as middle and working class areas.
The site of the explosion was not close to any embassies, some of which had been threatened by jihadists over the past few years.