Gausman started the 2013 season with the Double-A Bowie Baysox until the Orioles promoted him to the major leagues to make his debut in Toronto against the Blue Jays on May 23, 2013. In his debut against the Blue Jays, Gausman pitched five innings and allowed seven hits, four runs and two walks, also adding five strikeouts. Gausman picked up the loss as the Orioles fell 12-6 to the Blue Jays. On June 14, Gausman was optioned to the Triple-A Norfolk Tides. He was recalled on June 24. On June 28, Gausman earned his first Major League win, against the Yankees, pitching in relief of T. J. McFarland, going 4 1/3 innings, striking out four and allowing no walks and three hits. He was optioned back to Norfolk on July 10. He was again recalled from the Norfolk Tides on August 28, and earned his second big league win on September 1, also against the Yankees, but at Yankee Stadium.
On June 7, 2014, Gausman earned his first win as a starting pitcher, going 7 innings against the Oakland Athletics, allowing only 1 run, walking 1, and striking out 6. Following the best outing of his young career, Gausman pitched against the AL East leading Toronto Blue Jays where he went 6 Innings, again allowing 1 run and striking out three. In the 2014 postseason, Gausman pitched out of the bullpen for the Orioles.
Gausman throws five pitches, all with above average velocity: a four seam fastball at 96–99 miles per hour (154–159 km/h) (tops out at 101 miles per hour (163 km/h)), a sinker at 93–96 miles per hour (150–154 km/h), a slider at 83–86 miles per hour (134–138 km/h), a splitter at 84–86 miles per hour (135–138 km/h), and a changeup at 84–89 miles per hour (135–143 km/h).