Trailing 2-1 and facing double break point on her serve, Halep suddenly raised her standards, reeling off the next nine games in a row to clinch the opening set and jump out to a 4-0 lead in the second.
Kvitova, who won the New Haven Open last year, briefly threatened a comeback by winning two of the next three games before Halep closed out the match with an ace.
The 21-year-old Romanian captured the first WTA title of her career at Nurnberg in mid June but has been on a hot streak ever since.
She also won titles at 's-Hertogenbosch and Budapest and her first Premier-level success catapulted her into the top 20 for the first time when the new world rankings are released on Monday.
(Reporting by Julian Linden in New York; editing by Gene Cherry)
