The incident took place late on Monday on Lake Mariout, a brackish lake near the Mediterranean city of Alexandria.
The state-run al-Ahram daily reported the boat was carrying at least 19 people, all from the same family.
Among the dead were three children as well as two women, the report said.
Six people have been rescued and taken to a hospital while rescue workers continue searching for others who are still missing.
It was not immediately clear what caused the capsizing, but governor Mohamed el-Sharif said the boat was small and overcrowded.
He added that most boats on the lake work without licenses.
“The number of those missing has not been specified. We are here and prepared with four rescue teams which are already working now and another four ambulances," said Mr el-Sharif.
Relatives spent the night on the shoreline, hoping their loved ones could be rescued or their bodies retrieved.
Last July, 11 people drowned at a beach in Alexandria after a crowd tried to rescue a young boy ran struggling in the water .
A man jumped in to rescue him and became caught in the waters as did nine others who followed.
