Bruce Levine of 670 The Score was the first to report the deal.
The Tigers will receive minor league pitchers Michael Fulmer and Luis Cessa in exchange, reports Joel Sherman of the New York Post. Fulmer is ranked by MLB.com as New York's No. 7 prospect, while Cessa is No. 16.
Cespedes was the subject of numerous trade rumors leading up to the 4 p.m. ET MLB trade deadline on Friday.
Cespedes, 29, is hitting .293 with 18 home runs and 61 RBIs in 102 games this season.
Entering Friday, the Mets' offense has scored the fewest runs of any team in baseball (363) and has the lowest team batting average (.235) in the league.
New York hosts the Washington Nationals on Friday. The Mets are currently three games behind the Nationals for first place in the NL East.
- Molly Geary