Solomon did not play a minor league game in 2020 due to the cancellation of the minor league season caused by the COVID-19 pandemic. The Astros added Solomon to their 40-man roster after the 2020 season.[8] On April 17, 2021, Solomon was promoted to the major leagues for the first time.[9] He made his MLB debut the next day, pitching a scoreless inning of relief against the Seattle Mariners. Solomon picked up his first win on September 19, 2021, after working four innings in relief against the Arizona Diamondbacks, a game in which the Astros won 7–6.
On October 5, 2021, Minor League Baseball announced that Sugar Land Skeeters right-hander Peter Solomon was named the Triple A West Pitcher of the Year.[10]
On September 4, 2022, Solomon was claimed off waivers by the Pittsburgh Pirates and optioned to the Triple-A Indianapolis Indians. In 4 games (3 starts) for Indianapolis, he registered an 8.53 ERA with 10 strikeouts in 12+2⁄3 innings pitched. On November 10, Solomon was removed from the 40-man roster and sent outright to Triple–A.[12]
Arizona Diamondbacks
On December 7, 2022, the Arizona Diamondbacks selected Solomon in the minor league phase of the Rule 5 draft.[13] He was selected to the Major League roster on April 9, 2023.[14] Solomon made 5 appearances for the Diamondbacks, struggling immensely to a 12.15 ERA with 6 strikeouts in 13.1 innings pitched. On May 29, he was designated for assignment by Arizona following the activation of Kristian Robinson.[15] He cleared waivers and was sent outright to the Triple-A Reno Aces on June 2.[16] On October 3, Solomon elected free agency.[17]