Reports have linked the former Chelsea manager with a move to Eastlands at the end of the season to replace Italian tactician Roberto Mancini.
However, Mourinho said to Sky Italia: "Me to Manchester City? That's impossible."
Mourinho has always expressed his wish to return to the Premier League in the future.
However, the 48-year-old has three years left on his contract with Real Madrid and intends to honour it.
Mourinho was also asked about AC Milan's interest in Real star Cristiano Ronaldo.
AC Milan owner Silvio Berlusconi publicly expressed this week an interest in acquiring the Portuguese forward.
"I'm not saying it's impossible, because in football you never know, and Berlusconi can make a crazy offer," Mourinho said.
"But it must be a crazy offer because Real don't want to sell Cristiano Ronaldo."