The match was a reunion for Everton manager Marco Silva and Richarlison, who were both with the Hornets last season.
The Toffees took the lead in the 13th minute when Richarlison fired past Ben Foster after being picked out by Andre Gomes.
Watford hit back after the hour through a Seamus Coleman own goal before Abdoulaye Doucoure made it 2-1 moments later.
Everton were handed a chance to level matters in the 67th minute from the penalty spot, but Gylfi Sigurdsson's effort was saved by Ben Foster.
The hosts left it late to secure the equalsier as Lucas Digne found the back of the net with an impressive free-kick.
Athletic Bilbao 1-0 Girona
Athletic Bilboa struck in the dying stages of the second half to secure a 1-0 win over Girona to boost their survival hopes.
Veteran striker Aritz Aduriz got the winning goal from the penalty spot in the second minute of time added in the second half.
Despite picking up three points, Bilbao remain in 17th spot but are now level on points with 16th-place Villarreal.