Harriet Dart's US Open campaign ended in the second round after a disappointing loss to Ukrainian 19th seed Marta Kostyuk, with a score of 7-6 (10-12), 6-1. Despite having opportunities to win the first set, Dart was unable to convert five set points during a lengthy tiebreak, ultimately leading to her defeat in the second set as Kostyuk took control of the match. The match was played under extreme heat conditions, reaching 38 degrees Celsius, which seemed to affect Dart's performance. Dart had previously expressed enjoyment in having her mother as her coach for the tournament, following a strong first-round win against Chloe Paquet. With this defeat, Dart matches her best performance at the US Open but is set to achieve a career-high ranking in the low 60s. She was the only British player in singles action on the day, as her compatriots prepared for their matches in the tournament.