Martinez will get $12.5 million a year with Detroit to join fellow Venezuelan Miguel Cabrera in the Tigers' lineup.
"It's official," agent Will Polidor said. "Victor passed the physical and he'll be back in Venezuela today."
The agreement was first reported on Tuesday by ESPNdeportes.com contributor Ignacio Serrano.
The Tigers officially announced the deal on Friday morning, as general manager Dave Dombrowski said he expects Martinez to be used as a designated hitter while also catching two to three times a week.
"He also has the ability to fill in at first base and his versatility allows us to keep a premier bat in our lineup every day," Dombrowski said.
Martinez said Tigers slugger and fellow Venezuelan Miguel Cabrera contacted him about the possibility of teaming up in Detroit.
"He did make a few phone calls, and I expressed to him the desire that I wanted to make it happen," Martinez said Friday on a conference call. "It is a great organization."
Martinez, who turns 32 next month, hit .302 with 20 home runs and 79 RBIs with the Red Sox last season. He missed 35 games due to injuries.
Enrique Rojas is a reporter and columnist for ESPNdeportes.com and ESPN.com. Information from The Associated Press was used in this report.