An essay called "Heart of a Raven" on the NFL team's website revealed the story on Friday.
Reuland died on December 12 at the age of 29 after experiencing a brain aneurysm.
His heart went to former major league great Carew, who was at the top of the donor list after life-threatening complications from a heart attack he initially sustained more than a year earlier.
Carew met Reuland's mother three months after receiving the heart from Reuland, who played four games for the Ravens last season.
Mary Reuland greeted Carew with a hug and said, "You're part of our family now."
"Forever," Carew replied, according to the Ravens' website. "I will take care of this one because I've been given a second chance, and God knows how I feel and what I'm going to do for him."
Carew, 71, suffered a heart attack while playing golf in Corona, California, on September 20, 2015.
He underwent six hours of surgery and was near death. He also underwent a procedure to remove blood clots in his brain and had a device attached to assist his heart in circulating blood because it no longer functioned fully.
Carew also had a kidney transplant.
Carew started the Heart of 29 campaign -- 29 was his jersey number during his standout career with the Minnesota Twins and Angels -- to bring awareness to heart disease and help with prevention.
Carew, an 18-time All-Star, spent 12 seasons with the Twins and seven with the Angels during a career that ended in 1985. He won seven American League batting titles and was named AL Most Valuable Player in 1977 when he batted .388 for the Twins.
Carew finished his career with 3,053 hits and a .328 batting average. He was inducted into the Hall of Fame in 1991.