The former Atletico Madrid striker completed his transfer yesterday.
Gameiro has penned a three-year deal and says: "It was not easy, but as the president has said, it has long been clear in my head [that he wanted to join Valencia]. "Now I'm here and I'm very happy.
"A long time ago I wanted to come here, but because of club problems it couldn't be. Then there was no option and I went somewhere else.
"The coach [Marcelino García Toral] told me that he wanted to work with me for a long time. When the coach tells you that, it gives you a lot of confidence to come. I will work hard to try to do many great things here."