The deal is for $7.25 million, a source said. The agreement is pending results of a physical next week.
Young, 30, is a career .235 hitter with 144 home runs in parts of eight seasons with the Arizona Diamondbacks and Oakland Athletics. He made the National League All-Star team with Arizona in 2010. This past season, Young slumped to .200 with 12 home runs in 107 games with the A's.
The Mets have not commented on which outfield position Young, who hits from the right side, would play. He has appeared in 905 games in center field, 26 games in right and 24 games in left during his major league career.
The hope is that Juan Lagares hits enough to play center field, pushing Young to a corner spot. But Young would be capable of stepping into center field if needed.
Currently, the Mets' outfield alignment would be Eric Young Jr. in left field, Lagares in center and Chris Young in right. The Mets, however, still hope to add another outfield bat via free agency or trade, which could push Young Jr. to a fourth outfielder role or second base if Daniel Murphy were traded.
The Mets have been linked to free agent Nelson Cruz, but his salary demands exceed the Mets' appetite, according to a source. The Mets also have had dialogue with the Milwaukee Brewers about a trade that could send Ike Davis for an outfielder, although a Mets official recently insisted there has been zero dialogue about Ryan Braun.
The Boston Red Sox were among the other teams who had expressed an early interest in Young.
CBS Sports.com was first to report that Young had agreed with the Mets.