The person spoke on condition of anonymity Monday night because the deal had not been completed and the club had not made an announcement.
Several media outlets reported earlier that the sides had reached an agreement, which is reportedly for about $50 million over four years.
Jimenez went 13-9 with a 3.30 ERA in 32 starts for Cleveland last season. He turned down a $14.1 million qualifying offer from the Indians, so Baltimore would have to forfeit its first-round draft pick (17th overall) to sign him.
Orioles executive vice president Dan Duquette has been searching for a veteran starter for much of the offseason to help anchor the rotation. Jimenez is 82-75 with a 3.92 ERA over eight major league seasons.
The 30-year-old right-hander broke into the majors with Colorado in 2006. His best season was 2010, when he went 19-8 with a 2.88 ERA in 33 starts for the Rockies.