Officials say the number of dead is at least 41, with dozens injured. Children are believed to be among the dead.
An electrical fire broke out as 5,000 worshippers gathered for Mass at the Coptic Abu Sifin church in Giza, security sources told Reuters.
The fire blocked an entrance, causing a stampede, they said.
Fire services say the blaze has been brought under control.
The exact cause of the fire is not clear.
