Bouchard, the No. 1 seed at the grass-court event, fell to Kazakhstan's Yaroslava Shvedova, the world's 76th-ranked player, 6-4, 1-6, 6-4.
It was the ninth defeat in 10 matches for the struggling Bouchard, who also lost in the first round of the French Open, where she was seeded sixth.
In the new WTA singles rankings released Monday after the conclusion of the French Open, Bouchard dropped to 11th.
The Westmount, Que., native climbed as high as fifth last year, when she reached the semifinals in three of the four Grand Slam events, including the final at Wimbledon.