The former Porto, Sporting and Tottenham Hotspur player passed a medical in the morning and will be expected to help fill the gap left by last season's top scorer Roberto Soldado who has signed for Spurs.
Spanish media reported the deal was worth around 3 million euros (£2.58 million).
"I'm not the replacement for anyone. Every player is different," the 31-year-old told reporters. "Roberto was an important figure at Valencia in recent times but this is a new era."
Valencia finished fifth in La Liga last season to qualify for the Europa League.
(Reporting by Mark Elkington, editing by Brian Homewood)
