The 19-year-old forward put pen to paper on a contract tying him to Valencia until June 30, 2021 on Saturday after passing his medical with Los Che.
Mina came up through the youth ranks at home-town club Celta before making his Primera Division debut in February 2013. Last season he scored seven times in La Liga as well as two in the Copa del Rey.
He said on valenciacf.com: “It’s like I’m in a dream. To come to a great club like Valencia at such a young age isn’t easy, I know the responsibility that I have.
“I’m going to fight every day to return the confidence Valencia have placed in me and my goal is to help my team-mates and coach to continue being one of the best teams in Spain.”