Ighalo played a key role in helping the Hornets earn automatic promotion to the top flight last term and has further enhanced his reputation in the Premier League.
The Nigeria international has bagged eight times this season with his latest strike coming in the victory over struggling Aston Villa on Saturday.
The 27-year-old has revealed that he considered leaving Watford at the end of 2014-15 after receiving a big offer to switch to the Chinese Premier League.
Ighalo said: "I got a big money offer to join a Chinese team. But I don't think everything has to come down to money.
"I may not be as wealthy as Cristiano Ronaldo or Messi but I've worked hard for this team and this is my dream. The club sent their representatives and they met with our directors in London.
"I couldn't sleep for three days but knowing how I helped the team gain qualification from the Championship, I could not leave."
