The Philadelphia Phillies selected Vierling in the fifth round of the 2018 Major League Baseball draft, and he made his MLB debut with them in 2021.

Vierling, a senior, had been moved from his usual fielding position of outfielder to shortstop, next to his brother, a sophomore, at second base.

[4] Vierling was selected in the 30th round of the 2015 Major League Baseball draft by his hometown St. Louis Cardinals, but did not sign with the team and honored his commitment to the Notre Dame Fighting Irish.

As a sophomore, he batted .330 with seven home runs and 42 RBIs and was named third team All-Atlantic Coast Conference (ACC).

He was promoted to the Class AAA Lehigh Valley IronPigs after hitting .345 with 6 home runs and 16 RBIs in 24 games with Reading.

[15] He made his Major League debut that day as a pinch hitter, hitting a single to right field in his first at-bat off of San Francisco Giants reliever Jarlin García while also stealing second base and scoring a run.

On June 7, 2022, he was recalled to the Phillies from AAA affiliate, Lehigh Valley Iron Pigs, and hit the game-winning home run off of Josh Hader.

[20] On September 21, 2022, Vierling went 5-for-5, including his first walk-off hit in the 10th inning, in a 4–3 win against the Toronto Blue Jays, halting a five-game losing streak.