The 37-year-old has moved to Griffin Park on a one-year deal, and the club's sporting director Mark Warburton has hailed the signing of the former Levante full-back.
Warburton told the club's official website: "This is a signing that brings a wealth of experience and ability to the squad. He has an outstanding reputation in Spain for his professionalism and approach to the game.
"Javi has, like all our signings, been put through a rigorous testing procedure and we are delighted to see how well he performed and how clear his ambition is to take on a new challenge of the life presented by Brentford.
"This is a very different signing and is a coup for us. We are looking to expand our recruitment network and add value to the squad."
Venta was part of the Villarreal side that were defeated by Arsenal in the 2006 Champions League semi-finals.