Etebo joined the Hornets on loan from Championship side Stoke City until the end of the season with an option for a permanent deal.
He becomes the second Nigerian to sign for the team in this window and the fifth Nigerian at the club.
“I’m happy to be here with Watford and I hope that the season will be great for us. I’m looking forward to joining the group, it is a new challenge and I’m ready to move forward with the team”, he said in short messages posted on Watford’s Twitter handle and his Instagram page.
Etebo played for Turkish Super Lig side Galatasaray last season.