Also, on Friday, the Marlins outrighted catcher Kyle Skipworth to New Orleans.
Skipworth was designated for assignment on Wednesday to make room on Miami's 40-man roster for third baseman Casey McGehee, who signed a one-year contract worth $1.1 million.
Skipworth cleared waivers, and now he will open the season at Triple-A.
Valdespin is a left-handed-hitting outfielder who spent the past two seasons with the Mets.
A native of the Dominican Republic, Valdespin is a career .219 hitter with 12 home runs and 42 RBIs in 160 games.
Non-tendered by the Mets, Valdespin, who was suspended 50 games in August for being linked to the MLB Biogenesis probe, became a free agent on Dec. 2.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro. This story was not subject to the approval of Major League Baseball or its clubs.