The world No.2 was playing in his first final on grass, and took just 63 minutes to win 6-4 6-2 and warm up for Wimbledon in emphatic fashion.
It brings up Medvedev's second title of the season and his 11th in total, though he had failed to progress beyond the quarter-finals in his last five tournaments since winning in Marseille in March.
Medvedev suggested he was clicking into gear after his win over Pablo Carreno Busta on Saturday (AEST), and he backed up his point on Sunday (AEST), cruising to victory without offering up a single break point.
The 25-year-old broke world No.60 Querrey – seeking his first ATP Tour title since 2017 – on three occasions, and an ace, his 10th of the match, sealed victory.
Like at the French Open, Medvedev heads to Wimbledon as the No.2 seed.
He is the same half of the draw as 20-time grand slam champion Roger Federer, and has a first-round encounter with Jan-Lennard Struff, who knocked the Russian out of the Halle Open last week.