His exceptional career began in high school, where he wrestled for Hilton High School and achieved the rare distinction of becoming one of just seven four-time New York state champions. Diakomihalis concluded his varsity high school career with an impressive 210-match win streak, contributing to a remarkable overall record of 243-3. Notably, he secured Cadet World Championships in both 2015 and 2016, setting a high standard for age-group wrestling before committing to Cornell University in 2014. During this period, he was a four-time EIWA Champion (2018, 2019, 2022, 2023), and earned accolades such as Ivy League Wrestler and Freshman of the Year in 2018, Amateur Wrestling News Rookie Wrestler of the Year in 2018, and Ivy League Wrestler of the Year in 2019, 2022, and 2023.
He was also recognized as the EIWA Most Outstanding Wrestler in 2019. Beyond his collegiate achievements, Diakomihalis has garnered significant international recognition in freestyle wrestling. He earned a silver medal at the 2022 World Championships (65 kg), solidifying his status on the global stage. He is a two-time Pan American Champion, securing titles in 2020 and 2023, both at 65 kg.
Further international successes include winning the Henri Deglane Grand Prix (65 kg) and the Poland Open (65 kg) in 2021, the same year he became a US World Team Member (65 kg). Continuing his professional trajectory, Diakomihalis remains a prominent figure in the wrestling circuit. He is a two-time U.S. national champion in freestyle wrestling, most recently capturing the US Open Championship at 70 kg in 2025.
In the same year, he also secured the Real American Freestyle Lightweight Champion title, demonstrating his versatility and dominance across various weight classes and formats of the sport.