In July 2019, he signed with the Philadelphia Phillies as an international free agent. He made his professional debut in 2021 with the Rookie-levelFlorida Complex League Phillies before being promoted to the Low-AClearwater Threshers. He was placed on the injured list with a left elbow injury on 20 August and missed the remainder of the season and a portion of the following season, which he spent exclusively in the Florida Complex League.
Aldegheri returned to Clearwater for the start of the 2023 season before being promoted to the High-AJersey Shore BlueClaws on 3 August. After the 2023 season ended, his control was ranked the best in the Phillies farm system by Baseball America. Aldegheri returned to Jersey Shore for the start of the 2024 season.
Los Angeles Angels
On 27 July 2024, the Phillies traded Aldegheri and George Klassen to the Los Angeles Angels in exchange for Carlos Estévez. On 29 August, the Angels called Aldegheri up to the major leagues for the first time. While other Italian-born pitchers had previously appeared in the major leagues, such as Marino Pieretti, Aldegheri became the first pitcher born and raised in Italy to appear in an MLB game, when he made his debut with the Angels on 30 August. In three starts during his rookie campaign, Aldegheri posted a 1–2 record and 4.85 ERA with 10 strikeouts over 13 innings of work.
Aldegheri was optioned to the Triple-A Salt Lake Bees to begin the 2025 season. On 2 June 2025, he was recalled from Double-A Rocket City to join the major league club, where he pitched in one game, allowing two unearned runs across 2+1⁄3 frames, before being sent down again. Aldegheri made four appearances (including two starts) for Los Angeles during the regular season, logging an 0-2 record and 7.90 ERA with 12 strikeouts across 13+2⁄3 innings pitched.
Aldegheri was again optioned to Triple-A Salt Lake to begin the 2026 season.
Aldegheri was called back up to the Angels on 7 June 2026 to replace Jack Kochanowicz who was placed on the 15-day IL.
International career
Aldegheri pitched with the Italian national team at the 2018 Prague Baseball week; his performance there made a good first impression on scout Claudio Scerrato, who signed him to a contract with the Phillies organization.
He was named to the Italian square at the 2026 World Baseball Classic, one of three native-born Italians to make the team's WBC roster (the others being Gabriele Quattrini and Claudio Scotti), and the only one with MLB experience. Aldegheri pitched 4.2 scoreless innings with eight strikeouts in Italy's 8-0 shutout over Brazil, becoming the first pitcher born and raised in Italy to make a start for the Azzurri in WBC play. Starting Italy's quarterfinal matchup against Puerto Rico, he lasted 1.1 innings and allowed a lead-off homerun to Willi Castro before being relieved in the second inning. Over the course of his two starts in the tournament, Aldegheri posted a 3.00 ERA with 2 earned runs in six innings of work.
