As a result of her maiden title, the 484th-ranked Montgomery will move up to 240th in the WTA rankings on Monday ahead of the second Grand Slam of the season on grass at Wimbledon.
Montgomery, 21, had been ranked at a career-high 95th in June 2025.
The 30-year-old Krejcikova, who won the French Open in 2021 and Wimbledon in 2024, had been seeded eighth and was attempting to win her first title of the season in a first-time matchup against the American.