Kapler received a three-year contract to replace Bruce Bochy, who retired at the end of the season following 13 years and three championships with San Francisco.
The Giants made the announcement late Tuesday and planned a formal introduction Wednesday afternoon at the ballpark. Kapler is the second big hire in a matter of days by Giants president of baseball operations Farhan Zaidi, who on Monday introduced new general manager Scott Harris, most recently an assistant GM for the Chicago Cubs.
The 44-year-old Kapler was fired Oct. 10 after going 161-163 in two seasons with the Phillies. With slugger Bryce Harper their blockbuster acquisition, the Phillies finished 81-81 this year for their first non-losing season since 2012.
Zaidi and Kapler are now reunited from their time with the Los Angeles Dodgers, with whom Kapler served as director of player development and Zaidi the general manager.
Harris said he was impressed with the reference checks done on Kapler around the game. The Giants also received feedback from current San Francisco players.
Still, there will be scrutiny.
The Washington Post reported in February that Kapler did not alert police of an alleged assault by one of his Dodgers players in 2015. The newspaper said Kapler received an email from a 17-year-old girl saying she had been assaulted during a night of partying with two Los Angeles minor leaguers. Kapler tried to arrange a dinner with the girl and the two players, and engaged in discussions with the girl's grandmother, but he never alerted authorities. Kapler told the newspaper his actions were in line with club policy and advice offered by the Dodgers' lawyers and human resources personnel. He also said he was not aware of the assault allegation.
Zaidi said Tuesday he wishes he had handled the matter differently.
"We've had the opportunity to talk to people in the community and talk to experts to try to learn and understand what we did and what we did wrong," Zaidi said. "As I've had time to reflect on it, I've realized the biggest mistake we made was asking the wrong questions. In those situations, we asked, 'What do we have to do?' instead of 'What is the right thing to do?'
"I can only speak for myself, I'm truly sorry that from my perspective I didn't ask the right questions and address things appropriately."
A former outfielder, Kapler played parts of 12 major league seasons with six teams and was a career .268 hitter.
Bochy announced in February at spring training that he would retire after the season. He managed the Giants to World Series championships in 2010, '12 and '14. San Francisco went 77-85 in his final year.
Kapler has big shoes to fill. Bochy followed Felipe Alou and Dusty Baker in the job -- all beloved in the Bay Area.
"Gabe's someone obviously I worked with for three years and got to know personally and obviously know very well from a professional standpoint," Zaidi said. "I feel really optimistic and confident that once our fan base gets to know him, they're going to know the person I've known personally and professionally and be really excited about him as our next manager. There have been some portrayals of him publicly that I don't even recognize."
The club could look quite different heading into 2020 with lefty ace and 2014 World Series MVP Madison Bumgarner among baseball's top free agents.