While a student at Stevenson High School in suburban Chicago, Jaeger was the top ranked player in the United States in the 18-and-under age group. She won 13 U.S. national junior titles, including the most prominent junior titles in tennis: the 1979 Orange Bowl and 1979 Boca Raton.
In 1980 (at the age of 15 years, 19 days), she became the youngest player ever to be seeded at Wimbledon, a record that was broken by Jennifer Capriati in 1990. After defeating former champion Virginia Wade, she became the youngest quarter-finalist in the history of the tournament. Later in the year, she became the youngest semifinalist in US Open history.
In 1981, Jaeger won the U.S. Clay Court Championships, defeating Virginia Ruzici in the final.
At the French Open in 1982, Jaeger defeated Chris Evert in a semifinal 6–3, 6–1 but lost the final to Martina Navratilova. She then reached the semifinals of both the US Open and the Australian Open, losing both matches to Evert in straight sets.
At Wimbledon in 1983, Jaeger defeated six-time Wimbledon singles champion Billie Jean King 6–1, 6–1 in a semifinal on Centre Court, which was King's last career singles match at that tournament and her most lopsided singles defeat ever at Wimbledon. Jaeger then lost the final to Navratilova. In 2003, Jaeger said that the night before the final, she had a heated argument with her father over practicing and was locked out of her apartment by him. Eventually, Jaeger asked Navratilova to convince her father to let her back in. She stated that emotional fatigue might have contributed to her lackluster performance in the final. On July 4, 2008, Jaeger claimed in the British paper The Daily Mail that she threw the final against Navratilova.
Jaeger competed in the tennis demonstration event at the 1984 Summer Olympics in Los Angeles (tennis was re-introduced as an Olympic sport in 1988). In 2006, Jaeger exchanged gifts with an Army Ranger serving in the Iraq War. He gave her his dog tags, and she gave him her Olympic ring.
Jaeger's career win-loss record against other top players was 3–17 against Evert, 4–11 against Navratilova, 2–8 against Tracy Austin, 6–8 against Hana Mandlíková, and 2–4 against Pam Shriver.
In an interview in 2003, Jaeger stated that she was never committed to being the top ranked player in the world and tanked matches to avoid the top spot. As she rose toward the top of the game, she started visiting hospitals during tournaments. She stated that she found it, in the words of a USA Today columnist, "difficult to reconcile the narrow-minded focus of a top tennis player with her desire to help others."
Jaeger won eight of the nine singles matches she played for the U.S. in Fed Cup. She also won two of the three Wightman Cup singles matches she played for the U.S.
A major shoulder injury at the age of 19 ended Jaeger's career prematurely in 1985. Seeing this career-ending injury as a door to a spiritual awakening, she went to college and obtained a degree in theology.
Jaeger used her winnings from tennis to create the Silver Lining Foundation with her close friend and business partner Heidi Bookout in 1990. Located in Aspen, Colorado, the organization transported groups of young cancer patients to Aspen for a week of support and activities, including horseback riding and whitewater rafting. The foundation also provided money for reunions, family campouts, college scholarships, medical internships, and other programs for children who could not travel. The organization had other powerful backers, both in the world of sports and elsewhere. The first contributor was John McEnroe. Many high-profile celebrities were also involved, including Andre Agassi, Pete Sampras, and David Robinson. In 1996, Jaeger received the Samuel S. Beard Award for Greatest Public Service by an Individual 35 Years or Under, an award given out annually by Jefferson Awards.
Jaeger's autobiography, First Service, was published in 2004. In the book she wrote about her teenage years as a tennis player and her later decision to focus on serving God. All proceeds from the book were donated to children's charities.
Jaeger has since established the "Little Star Foundation", reaching on average 4,000 kids annually. She has moved from Aspen to a much larger 220-acre (0.89 km2) property in Hesperus, Colorado, where she will be able to expand her programs.
On September 16, 2006, at the age of 41, Jaeger became Sister Andrea, an Anglican Dominican nun. She reportedly left the order in 2009.
In April 2007, Jaeger and several former athletes, including Andre Agassi, Lance Armstrong, Tony Hawk, Jackie Joyner-Kersee, and Muhammad Ali, appeared on the American morning television talk show Good Morning America to announce their formation of a new charity entitled "Athletes for Hope" with the goal of encouraging their fellow athletes to think philanthropically.
Oprah Winfrey describes Jaeger as a superstar turned superhero.
SR = the ratio of the number of Grand Slam singles tournaments won to the number played.