Withrow and Sock received a wildcard for the 2017 Cincinnati Masters doubles tournament, where they lost to Juan Sebastián Cabal and Fabio Fognini in the first round.

He won his first ATP level doubles match with partner Austin Krajicek at the 2017 US Open by defeating Philipp Oswald and André Sá in the first round.

Withrow and Sock made a doubles run to the title at the 2018 Delray Beach Open, first defeating Leander Paes and Purav Raja in the first round.

At the 2019 Australian Open he reached the third round with Jack Sock, defeating second seeded pair and previous year finalists Juan Sebastián Cabal / Robert Farah on the way.

[3] At the 2019 US Open, partnering Sock, he reached his first Grand Slam quarterfinal defeating the Bryan brothers en route but lost to 15th seeded pair of Jamie Murray/Neal Skupski.

Withrow and Lammons won their sixth title as a pair at the 2024 Libéma Open defeating top seeds Wesley Koolhof and Nikola Mektić.

[16] At the US Open Withrow reached the semifinals of a Grand Slam for the first time in his career, partnering Lammons, with wins over three-time defending champions Joe Salisbury and Rajeev Ram[17] and 13th seeds Wesley Koolhof and Nikola Mektić.

[19] At the 2024 Shanghai Masters, they reached the quarterfinals but lost to Wesley Koolhof and Nikola Mektić which halted their attempt to move one position up above their opponents in the ATP doubles race from their current place of No.