D'Arnaud recently rejoined the first-place Braves after missing more than three months with a thumb injury. The extension includes an $8 million club option for 2024 with no buyout.
The streaking Braves finalized the extension before the start of a weekend series in Baltimore. They have now won 14 of 16 games -- including a season-best seven-game winning streak -- to build a four-game lead in the National League East.
D'Arnaud said he never had any desire to test his value on the free-agent market. The Braves wanted to keep d'Arnaud in the fold as well, and he immediately rewarded them by crushing a second-inning pitch from Keegan Akin (0-8) following a single by Dansby Swanson.
"I told him after the game, dude you're worth every penny,'' Braves manager Brian Snitker said. "The job he did with Max [Fried], too.''
D'Arnaud was delighted to be on the receiving end of Fried's masterful throws in the pitcher's first career nine-inning complete game, and relished the home run that made a wonderful day even more special.
"It blew my mind a little bit,'' d'Arnaud said. "It put us up 2-0 and that's all we needed. It was a real fun day.''
It was his second homer in five games since coming back from injury. D'Arnaud also had an infield hit and drew a walk.
In his first season with Atlanta in 2020, d'Arnaud batted .321 with nine homers and 34 RBIs, earning an NL Silver Slugger award as the top hitter at his position and helping the Braves win their third straight NL East title.
"He wanted to be here, and we wanted him to stay," general manager Alex Anthopoulos said. "It's a really good fit."
D'Arnaud needed surgery on his left thumb after suffering a torn ligament while making a tag in a May 1 game against the Toronto Blue Jays.
While d'Arnaud was out, the Braves went through five catchers without much success. William Contreras got the first shot filling in for d'Arnaud, but the 23-year-old struggled during an extended stint as the starter.
Contreras was sent back to Triple-A Gwinnett even before d'Arnaud had recovered from his injury, leaving the position in the hands of a revolving door of journeymen that included Stephen Vogt and the since-released Kevan Smith.
Anthopoulos said the signing of d'Arnaud gives prospects such as Contreras and Shea Langeliers -- the No. 9 overall pick in 2019 and currently at Double-A Mississippi -- a chance to develop without being rushed to the big leagues.
"Contreras and Langeliers are exceptionally talented. I think they're both going to be All-Stars at some point," Anthopoulos said. "But there's a lot more to that position than throwing guys out. It's about preparation, having guys on the mound that believe in you. Experience and reps are really critical at that position."
D'Arnaud said he is eager to mentor the catchers who could replace him some day.
"Both of them are going to be studs in this league for a long time," he said. "Hopefully they both know they can reach out to me anytime with any questions they have."
The Braves came within one game of reaching the World Series last year, squandering a 3-1 lead to the Los Angeles Dodgers in the NL Championship Series. D'Arnaud had two homers and 10 RBIs in 12 postseason games.
He signed a two-year, $16 million contract with the Braves ahead of the 2020 season after reviving his career in Tampa Bay.
D'Arnaud was released by the New York Mets early in the 2019 season and went to Tampa Bay after a brief stint with the Dodgers. He suddenly blossomed with the Rays, hitting .263 with 16 homers and 67 RBIs in 92 games.
As part of his new deal, d'Arnaud will donate 1% of his earnings to the Atlanta Braves Foundation.
Anthopoulos said other Braves players have a similar clause in their contracts, but it has never been publicized. He decided it was time to give his players credit for their role in improving the community.
"We live here. We care about this place," Anthopoulos said. "The more awareness we can bring to that, and knowing the players are doing their part, I think is a real important thing."
The Associated Press contributed to this report.