The meeting was held at the Anfield stadium in Liverpool and ended with a score of 2:0.
In the 53rd minute, the hosts took the lead thanks to an own goal by Pervis Estupinyan - the defender cut the ball into his own net after a cross from Jordan Henderson.
And in the 55th minute, Sadio Mane doubled the advantage of the Merseysiders, assisted by Mohammed Salah.
The return game between the teams will take place on May 3 in Villarreal.
Earlier, Liverpool head coach Jurgen Klopp shared his expectations for the match against Villarreal.