He played in MLB for the Tampa Bay Rays, Colorado Rockies, Los Angeles Dodgers, San Francisco Giants, Milwaukee Brewers, and Washington Nationals.

[3] McGee made his minor league debut in 2004, and spent 2004 and 2005 with the Princeton Devil Rays and the Hudson Valley Renegades.

[9] McGee made the Rays MLB roster after spring training in 2011, but he was sent down to the team's Class AAA minor league affiliate after 11 appearances.

After undergoing elbow surgery to remove "loose bodies" in December 2014, McGee spent the early portion of the 2015 season with the Class AAA Durham Bulls.

[12] On January 28, 2016, McGee and Germán Márquez were traded to the Colorado Rockies for Corey Dickerson and Kevin Padlo.

McGee and the Rockies avoided salary arbitration on December 3, 2016, by agreeing to a $5.9 million contract for the 2017 season.

[16] On February 17, 2021, McGee signed a two-year contract with the San Francisco Giants worth $7 million, with a club option for the 2023 season.

[19] McGee was named National League Reliever of the Month for July 2021, after not allowing a run in 11 innings and recording seven saves.

In 2022, McGee made 24 appearances for San Francisco but struggled to a 7.17 ERA with 11 strikeouts and 3 saves in 21.1 innings pitched.