Johnson is one of five seeded Americans slated to play this week. Two-time Newport champion and top-seeded John Isner, No. 4-seeded Jack Sock, No. 6 Sam Querrey and No. 8 Tim Smyczek are scheduled to play their opening matches later this week.
Johnson broke Berrer's serve in the third game of the second set to take control. Berrer failed to hold serve the rest of the set, then was broken two more times in the third. Johnson converted 6 of 9 break points.
''It showed a good bit of resilience on my part to come back,'' he said. ''It wasn't looking so great for the first hour.''
On match point, Johnson raced to the net and hit a shot that sailed past Berrer to clinch the victory.
He's hoping it set the stage for a good week for himself and his fellow Americans.
''We always want to win and help one another - winning breeds winning and confidence,'' he said. ''If I see John win - Jack, Sam, you name it, guys I train with - if they can do it, why can't I do it? We're all in the same place.''
He was wearing a neon yellow shirt and dark green shorts at the only grass-court tourney in North America and joked that ''I just wanted to blend in with the grass.''
No. 3-seeded Bernard Tomic was upset by fellow Australian John-Patrick Smith 6-3, 7-5. Second-seeded Ivo Karlovic of Croatia beat Illya Marchenko of the Ukraine 7-6 (4), 6-7 (4), 6-4.
The tournament is played in conjunction with induction ceremonies for the International Tennis Hall of Fame.
Two-time major champion Amelie Mauresmo of France heads the 2015 class that's scheduled to be enshrined during a center-court ceremony before the semifinals Saturday.
The 36-year old, who is now Andy Murray's coach, won the Australian Open and Wimbledon in 2006 and spent 39 weeks at No. 1 in the WTA rankings. Mauresmo, hired to work with Murray last year, is pregnant and unable to travel to the ceremony.
Joining Mauresmo will be David Hall of Australia, a six-time Paralympic medalist, and Nancy Jeffett, elected in the contributor category.
In other matches, Jared Donaldson beat fellow American Austin Krajicek, 6-7 (5), 6-3, 6-2; Alejandro Falla, from Columbia, defeated Adrian Mendez-Maceiras of Spain 6-1, 7-5; and Japan's Tatsuma Ito beat American Noah Rubin, 6-3, 6-7 (4), 6-4.