Dayana Yastremska of Ukraine bounced the 29-year-old from Westmount, Que., 6-1, 4-6, 6-4 on Thursday at the USTA Billie Jean King National Tennis Center in New York.
Yastremska, who is the 12th seed, had six aces but also committed four double faults.
The 2014 Wimbledon finalist, Bouchard had three aces and also hit into three double faults.
In men’s qualifying, Vasek Pospisil from Vernon, B.C., is to play Zachary Svajda of the United States later Thursday.
Pospisil reached the second round with a 7-6 (7), 6-7 (3), 6-4 victory over Spain’s Pedro Martinez on Wednesday.
The main draw for the final Grand Slam tournament of the season begins Monday in Flushing Meadows, N.Y.
