Ioannis Kiriazis has competed in international javelin competitions since 2012. The following year started at the U18 World Championships in Donetsk, where he was eliminated from the qualification with a width of 69.39 m. In 2014 he was the Greek U20 champion and then took part in the U20 World Championships in Eugene. He came to 70.38 m in the final and finished seventh. After graduating from school, he then went to the United States and began studying at Texas A&M University . In 2015, he took part in a variety of national competitions for the university's sports team. In July he competed at the U20 European Championships in Eskilstuna, where he was fourth with 77.05 m.
In the summer of 2016, Kiriazis took part in the European Championships in Amsterdam. After 81.92 m in the qualification and the entry into the final, one day later he stayed more than six meters below the qualifying distance and thus finished twelfth in the final. In March 2017, he set his personal best in Austin with 88.01 m, which was the second largest distance ever thrown by a Greek in a competition and also promoted him to 44th place on the all-time world best list (as of April 2020). In July he threw in the final of the U23 European Championships in Bydgoszcz the javelin to 81.04 m, with which he won the silver medal. A month later he qualified for the final at the World Championships in London, where he finished sixth with a width of 84.52 m.
Doping ban
In March 2020, Kiriazis was banned until May 2023 for taking the drug Ligandrol , which was proven in a doping test after a competition in College Station in April 2019. At the hearing in London, he stated that he was ignorant of the substance, but this was rejected.