Originally acquired from Seattle as a teenager in the Adam Lind trade, the right-hander—affectionately known as "Fastball Freddy” made his MLB debut for the Brewers in 2018.

In his 2018 debut at Coors Field, Peralta reached a summit of immediate impact by striking out 13 batters, the most ever by a Brewer in their first Major League start; however, it was not until the 2021 campaign that he established himself as a potential top pitcher in the game.  That season, he went 10-5 with a 2.81 ERA, earned his first All-Star selection, and held opponents to a staggering .165 batting average.

Peralta demonstrated commendable performance over the subsequent three seasons; however, in 2025, he emerged as a Cy Young Award contender. He functioned as the principal catalyst for a Brewers rotation that achieved a franchise-record 97 wins, concluding the season with a personal best of 17 victories and an impressive 2.70 ERA. Throughout this period, he exhibited comprehensive command of the mound, recording 204 strikeouts and receiving the National League Pitcher of the Month accolade in August following a remarkable streak that included 30 consecutive scoreless innings.

Following his fifth-place finish in the 2025 Cy Young voting and with only one year of team control remaining, the organization finalized a blockbuster trade that sent Peralta to the New York Mets.  In his eight seasons in Milwaukee, Peralta had a 71-45 record, a 3.58 ERA, and 1,195 strikeouts.