He replaced Abdoulaye Doucoure in the 88th minute as Benik Afobe’s 82nd minute strike ensured the hosts avoided defeat at home.
The 27-year-old has had a quite remarkable rise at Vicarage Road, scoring 36 goals for the Hornets since his move from Laliga.
Ighalo was brought to England from Granada in the summer of 2014. And he has gone on to become a key figure for Watford, playing in a variety of attacking roles due to his versatility.
Watford are currently 14th in the Premier League table. They face Arsenal at the Emirates Stadium in their next game on January 31.