"His reputation on and off the court are flawless and I look forward to getting to work," said Harrison.
This season has been the best of Harrison's career so far, and includes his first tour title at Memphis, a French Open victory in doubles, and reaching a career-high of No. 40 in singles. Harrison also married longtime girlfriend Lauren McHale, fellow pro Christina McHale's sister, following his win at Memphis.
Harrison is No. 47 in the rankings.
Naomi Osaka has also made a change to her team. She brought on Sascha Bajin, the coach announced.
Bajin was working with Caroline Wozniacki for most of this season as an assistant coach and hitting partner, having previously had a similar role with Victoria Azarenka and a long association with Serena Williams.