[4] He was a wrestler at Amherst College from where he graduated magna cum laude in 1977 with his bachelor's degree in economics.

[1] After graduating from Harvard Business School, he returned home to work at John Middleton Inc. where his father put him on the company's board.

[11] Subsequently, Nupson filed a malpractice lawsuit, on July 15, 2020, with the U.S. District Court for the Eastern District of Pennsylvania, alleging ethical misconduct by Schnader Harrison Segal & Lewis and attorney Bruce A. Rosenfield, who had represented her in the suit against her brother.

When Phillies' chairman David Montgomery took a medical leave of absence in 2014, Middleton assumed a more active role, overseeing on-field and business performance, and increased his shareholding to 48 percent.

Middleton committed that the Phillies would have a greater focus on analytics, which influenced the hiring of Andy MacPhail as president, and Matt Klentak as general manager.

[18][13] Middleton and his wife, Leigh, share philanthropic involvement in several organizations,[19] including the Philadelphia Museum of Art, Penn Medicine,[20] the Bryn Mawr Presbyterian Church,[21] the Academy of Natural Sciences, and Project HOME.