Jon Heyman of FanRag Sports first reported the news Sunday.
Kapler, 42, was serving as director of player development for the Los Angeles Dodgers. He held that role since 2014 but has no managerial experience. Analytics and nutrition were a major part of Kapler's push in Los Angeles, including eliminating junk food from clubhouses and serving organic food.
Kapler will replace Pete Mackanin, who went 174-238 in his three seasons. The Phillies announced Mackanin would transition to a front office role following the 2017 campaign.
"In my mind, we have reached a turning point in this rebuild," Phillies general manager Matt Klentak told reporters in September. "... It's time to look forward. That's the message today: It's time to look forward.
"I don't think we've reached the end of our rebuild, but I do think the worst part, the hardest part of our rebuild is in the rearview. I think as we look forward, as we continue to balance the present and the future, that we are getting closer to the point where the present is going to become more important."
The Phillies have not made the playoffs since 2011, undertaking a massive rebuilding effort that slowly stripped the payroll of high-cost, ineffective veterans. The roster is now youth-laden but talented, with Klentak hoping Kapler can tap into the potential.