The 34-year-old left-hander became a free agent after completing a $137.5 million, six-year contract with the New York Mets, who declined a $25 million option and paid a $5.5 million buyout.
Santana, 139-78 with a 3.20 ERA in 12 seasons with the Minnesota Twins and Mets, missed the 2011 season following shoulder surgery on Sept. 14, 2010, returned to pitch the Mets’ first no-hitter on June 1, 2012, then missed last season after an operation on April 2.
The deal announced Tuesday follows Baltimore’s recent agreements with right-handers Ubaldo Jimenez and Suk-min Yoon, as well as outfielder Nelson Cruz.