Mervis played college baseball at Duke University, and signed with the Cubs as an undrafted free agent in 2020.

[4] Mervis attended Georgetown Preparatory School in North Bethesda, Maryland, where he played baseball.

He earned a spot on the 2014 Perfect Game Preseason Underclassmen All American Team as a High Honorable Mention.

[9] That summer, he played with the Silver Spring-Takoma Thunderbolts of the Cal Ripken Collegiate Baseball League, and had a .411/.469/.643 slash line over 15 games, with his batting average leading the league and his on-base percentage (OBP) and on-base plus slugging (OPS) ranking third and second, respectively.

[16] During his junior season at Duke in 2019, he pitched in seven games in which he was 1–0 with a 2.16 ERA and eight strikeouts over 8+1⁄3 innings, while posting a .274/.358/.421 slash line with six home runs and 31 RBIs in 190 at-bats and 48 starts.

[9] Mervis went unselected in the five-round 2020 MLB draft, and signed with the Chicago Cubs in June 2020 as an undrafted free agent, as a first baseman.

[24][25] The Cubs named him their Minor League Player of the Month for August 2022, during which he batted .305 with a .390 OBP and a .926 OPS for Iowa.

[33][34] Mervis was selected to play for the Mesa Solar Sox in the 2022 Arizona Fall League.

[41][42] Mervis was promoted to the major leagues for the first time on May 5, 2023, and made his MLB debut that day, batting 7th and playing first base against the Miami Marlins.

Mervis hit his first major league home run on May 16 against the Houston Astros at Minute Maid Park.

On June 15, the Cubs optioned Mervis back to Triple-A Iowa after he hit .167/.242/.289 with 3 home runs in 90 at bats, while playing first base.