Querrey won his third title of the year, all on different surfaces — he won in Memphis on hardcourt and in Belgrade on clay.
"The conditions were pretty tough out there, the windiest day of the week so far," said Querrey, who hit 15 aces. "I just tried to stay level-headed and keep my composure, and fortunately I got through it.
"I didn't set a round (to reach), quarters or semis or anything like that. I just wanted to go out there, play with a good attitude, play level-headed and work on hitting my forehand inside out more than inside in, which I did a great job of all week."
Fish had three break points to go 2-0 ahead in the first set. But Querrey held him off with aces on the first two points and Fish netted a backhand on the third.
Games then went easily on serve, although Querrey was stretched to deuce at 6-5 before taking the set to a tiebreaker. Querrey won four consecutive points from 3-3 to take the tiebreaker.
Querrey then began the second set with four aces to hold the opening game in just 38 seconds.
Fish earned a break for 3-2 when Querrey ended a long rally by hitting a forehand long.
Fish failed to serve out the set at 5-4, allowing Querrey to even it after a backhand error. Fish was broken again for the match when he mis-hit a volley on Querrey's second match point.
Querrey is now looking forward to Wimbledon, which begins a week from Monday.
"I'm playing great on the grass, and now I've got a week to practice and regroup," he said. "I'd love to win Wimbledon. I'm kind of going with baby steps (to) try and make the third round this year, because the second round is the best I've ever done there.
"It's possible, but I think I've still got some work to do, and there's still some great competitors out there you have to beat to win a Wimbledon title."