His manager Quique Flores was also named Manager of The Month for December as they finished the year in ninth place.
The Hornets won their first three games in the month to climb the table and only lost their unbeaten record just after Christmas when they were beaten 2-1 by Tottenham, a result that came after a memorable 3-0 win over Liverpool and a fine 2-2 draw at Chelsea.
Ighalo was the star turn for the top-flight new boys, netting five times, including a brace in the 3-0 win over the Reds at Vicarage Road.
Advertisement
He beat the likes of Mesut Ozil, Marko Arnautovic, Riyad Mahrez, Romelu Lukaku and Dele Alli to the player award.
Watford are 11 points clear of Sunderland who occupy the final relegation place, and just seven points behind Spurs who sit fourth.
Though they began 2016 with back to back defeats against Manchester City and Southampton, Quique Flores side travel to relegation-threatened Swansea on Monday evening looking to get back to winning ways.