Germán made his first career MLB start on May 6, 2018, at Yankee Stadium against the Cleveland Indians. He pitched six innings without allowing a hit, allowing two walks and striking out nine batters. Germán was removed after the sixth inning due to his pitch count and not being completely stretched out as a starter yet. Germán became the first pitcher in MLB history with nine or more strikeouts and zero hits allowed in his first MLB start. In 19 games (13 starts), Germán had a 2–6 record and a 5. 68 ERA. He was optioned to Triple-A on July 21, 2018. In 2019, Germán made the Yankees' Opening Day roster. He was named 'Hurler of the Month' by the team after posting MLB-leading 5 wins, 2. 56 ERA (8th in AL), 0. 85 WHIP (2nd), 0. 177 BAA and 0. 470 OPS (both lead AL) in April. On June 9, 2019, German was put on the 10-day injured list due to a hip strain. He was activated on July 3, 2019. In his first start back from the IL, German allowed a home run by Jeff McNeil on the first pitch, but it was the only run he allowed in 6 innings as the Yankees won 5-1 against the New York Mets.