She plays right-handed with a double-handed backhand. Her highest junior ranking was no. 16 on September 12, 2011. She is one of the youngest tennis players to win a match on the WTA Tour, at the age of 14 years and 48 days, by beating world no. 81 Alla Kudryavtseva. Since the age of 9, Keys has been part of the Chris Evert Academy in Boca Raton. On July 7, 2014, Keys reached a career high ranking of number 27 in the world.
In 2011, Keys won a spot in her first US Open by beating Beatrice Capra in the finals of an eight-player wildcard playoff. Keys won her first match, beating world no. 111 Jill Craybas, but then lost in three sets to world no. 27 Lucie Šafářová.
In 2012, after winning a wildcard tournament against other American players, Keys qualified for the 2012 Australian Open, but lost to 2010 semi-finalist, Zheng Jie in the first round.
At the 2013 Mutua Madrid Open she notched up the biggest win of her career and her first victory over a top-ten opponent when she defeated world no. 5 Li Na in the first round. Keys played wildcard entry Anabel Medina Garrigues in the second round, but lost in straight sets 6–7, 3–6. At the French Open Keys beat Misaki Doi 6–3, 6–2, but lost to Monica Puig 4–6, 6–7.
At the Aegon Classic, Keys beat Lesia Tsurenko in the first round 3–6, 6–3, 7–6(7–3), compatriot Jamie Hampton 2–6, 6–3, 7–6(7–3) in the second round and 6th seed Mona Barthel 6–3, 6–2 in the third round. Keys lost to Magdalena Rybarikova in straight sets 3–6, 0–6 in the quarterfinals. However, just over a month later, on a hardcourt at the Bank of the West tournament in Stanford, she had her revenge, upsetting the eighth seed Rybarikova 6–2, 6–2 in the first round.
Keys plays right-handed, has powerful groundstrokes and dominant serves over 100 mph. Her service action is similar to that of American Lindsay Davenport. Due to the height of her ball toss she, at times, faces inconsistency on serve. She is primarily an offensive baseline player and her game is built around taking control of rallies with powerful serves, return of serves and forceful groundstrokes off both forehand and backhand wings. She is equipped with capable volleying skills and overheads. The 2014 season has seen a great improvement in Keys' mobility around the court and she has now an effective defensive game, being capable of turning defensive play in to offensive play. It has been suggested that her playing style is similar to fellow American Jennifer Capriati.
Many top players see Madison Keys as the greatest prospect in American tennis.
Keys first became interested in tennis because she liked tennis dresses, according to a video interview she conducted with World Tennis Magazine in August 2011. She also revealed that she is a fan of Roger Federer. Coached by Adam Peterson and Ola Malmqvist. Parents are Rick and Christine (attorneys); siblings are Sydney, Montana and Hunter. Introduced to the sport by parents. Favorite shot is serve; favorite surface is hard. Favorite food is ice cream; favorite drink is peach iced tea. Favorite actor is Julia Roberts; favorite movie is Titanic. Favorite singer is Britney Spears; favorite types of music are hip-hop, pop, rap and country. Favorite author is Stephanie Meyer. Also enjoys baking, seeing friends, watching TV and shopping. Favorite place to visit is Paris. Most memorable experience is playing a match in an earthquake in Costa Rica. Goal is to work hard and be the best she can be.