The Tigers announced on Tuesday they had signed Rodriguez to a five-year contract but did not disclose financial terms of the deal.
"Eduardo was clearly one of our top targets in this year's free agent pitching class, and we are extremely happy to add someone of his caliber to our rotation,'' Tigers general manager Al Avila said. "There are a number of strong qualities that Eduardo brings to our ballclub, including his leadership abilities, and we look forward to the positive impact he will have on our team both on and off the field.''
Rodriguez, 28, went 13-8 with a 4.74 ERA last season with the Red Sox after missing all of 2020 because of coronavirus-related myocarditis.
"I am excited to be a Tiger and appreciate the commitment being made to building a winning team in Detroit,'' Rodriguez said. "After some great years in Boston with amazing fans and teammates, I am blessed to be coming into a new situation where the fans in Detroit are some of the best in baseball.
"In speaking with Al and (manager) A.J. (Hinch), I knew this is a place that would be a good fit for me and my family. I can't wait to join my new teammates and work towards a World Series title," he said.
Rodriguez was Boston's best starter in 2019, finishing sixth in the American League Cy Young voting and posting a 19-6 record with a 3.81 ERA and 1.33 WHIP in 34 starts.
Boston made him an $18.4 million qualifying offer and will receive an additional pick in next year's amateur draft due to the deal with the Tigers.
In seven seasons in Boston, Rodriguez was 64-39 with a 4.16 ERA.
The Athletic first reported Monday that Rodriguez and the Tigers had finalized a deal.
The Associated Press contributed to this report.