The Elephant House in Edinburgh suffered smoke and water damage after a blaze broke out at the patisserie next door on Tuesday.
More than 60 firefighters and 12 fire engines were deployed to tackle the blaze. The Scottish Fire and Rescue Service said one of its crew members was taken to hospital as a precaution and later released.
Images showed the cafe with its front windows gone, a ruined interior and debris lying outside.
Owner David Taylor told the BBC he was “devastated” by the extensive damage to his business. He said the cafe would likely be closed for months for repairs.
The Elephant House is a regular stop for Harry Potter fans and long bore a sign declaring itself as the “birthplace” of the fictional young wizard.
Rowling has disputed that, saying she began writing the magical stories before she moved to Edinburgh. But she confirmed she frequented the cafe while penning some of the seven-book series.
The Patisserie Valerie, where Tuesday’s fire started, also was heavily damaged. Firefighters remained at the scene in Edinburgh’s Old Town with the street closed off into Wednesday.