The video was submitted to Visit Naples, the organisation that promotes tourism in Italy's third-biggest city.
Here's another video of people singing on their balconies.
And another filmed in Siena, Tuscany.
People are getting emotional watching the videos.
Many have compared it to when people in Wuhan, China, were in lockdown and sang the national anthem from their windows.
The Facebook page that posted the video also promoted an event titled "Flashmob: in concert from the balconies". The event is set to take place March 22, so it looks like more videos could be appearing soon.
Ikran Dahir is a reporter for BuzzFeed News and is based in London.