Pegula, daughter of natural gas billionaire Terrence Pegula , who owns the Buffalo Bills and Buffalo Sabers , started tennis at the age of seven and became a professional player in 2009.
She gained her first experience at smaller tournaments on the ITF Women's Circuit . Like many American players, she also took part in college competitions in which she represented the University of Pittsburgh . In 2010 she received a wildcard for the junior women competition at the US Open , but lost there in the first round. In the following year she was allowed to compete in the women's qualification competition in New York , where she won against Kiki Bertens before she was eliminated in the second round. In 2012 she was able to push herself into the top 200 in the world rankings for the first time after participating in the finals at major ITF tournaments in the $ 100,000 category in Marseille and Vancouver . In the same year she gave her her debut on the WTA Tour in Québec , where she subsequently moved into the main draw as a lucky loser , but lost there at the beginning against Petra Martić .
Again and again, injury concerns interrupted the American's progress and forced her to take longer breaks from professional tennis. Due to a knee injury, Pegula only played one ITF tournament in 2014, where she had to retire during their second round encounter. The following year she made her comeback on the ITF tour, but thanks to a protected ranking that allowed her to take part in larger ITF tournaments, she quickly made her way up the world rankings again. At the US Open 2015 she reached the main draw of a Grand Slam tournament for the first time and immediately won her first round match against Alison Van Uytvanck ; in the second round she had to admit defeat Dominika Cibulková in three sets. In 2016 she took part in three more semifinals on the ITF tour, before she was given a wildcard and entered the semifinals of a WTA tournament in Washington with her best career win against Samantha Stosur for the first time.
After an operation on the hip, Pegula was only able to return to the tour in August 2017. In Québec she reached her first WTA final the following year. On the way from qualification to the final, in which she was defeated by Pauline Parmentier , she beat the two seeded Petra Martić. In 2019, she was able to confirm the good form from the previous year, when she was stopped in the final by Bianca Andreescu at a tournament of the WTA Challenger Series in Newport Beach and then also reached the final at the highly endowed ITF tournament in Midland , but against Caty there McNally lost. Despite changeable results in the further course of the season, she experienced her greatest success so far in Washington by winning her first WTA title after a straight two-set win against Camila Giorgi . The following week Pegula achieved her best world ranking position with position 55.
In January 2020, she reached the third final on the WTA Tour in Auckland . After defeating Caroline Wozniacki in three sets in the previous round , she lost the final against Serena Williams 3: 6 and 4: 6.