Since leaving Borussia Dortmund in 2010, the 30-year-old has been much-travelled, initially enjoying spells at Hercules, Rubin Kazan and Valencia.
Valdez joined Al Jazira last year and scored four goals in 12 league appearances before being loaned out to Olympiacos, where he netted six times in 10 Greek Super League outings.
On Tuesday, Frankfurt confirmed the signing of Valdez and sporting director Bruno Hubner expressed his pleasure at the capture.
"With Nelson Valdez, we have a player for Eintracht Frankfurt who brings a lot of experience," Hubner told the club's official website.
"He has worked with [coach] Thomas Schaaf already [at Werder Bremen], very successfully.
"We look forward to working together."