In 1971 Mygiakis became Greek champion, was used in the featherweight division and, for the first time, participated in an international championship, the World Cup in Sofia. There Mygiakis, who was only 19 years old, lost both fights. In the 1972 European Championship in Katowice he had three wins and achieved sixth place. At the Olympic Games in Munich in 1972 he had three wins again, including one over the Soviet favorite, Jemal Megrelischwili, leading to a seventh place finish.
Over the next six years Mygiakis entered almost every European and World championship but never managed to win a medal. His best results were fourth place at the World Cup 1974 in Katowice, fifth place at the World Cup 1978 in Mexico City and sixth place at the European Championship 1975 in Ludwigshafen am Rhein, each as a featherweight. In all these international championships the top competitors, almost without exception, came from the Eastern Bloc countries.
In 1979, Mygiakis made a breakthrough. At the European Championships in Bucharest, although he lost in the second round against the Soviet wrestler Boris Kramarenko, thanks to three wins over the Turk Metin Eser, the Pole Kazimierz Lipień and Hungarian István Tóth, and fact that Kramarenko lost to Toth, he became the European champions.
The climax of Migiakis's career was the 1980 Olympic Games in Moscow. He beat, among others, Lipień and Tóth again, as well as Kramarenko, and was Olympic champion in spite of a double defeat against Lars Malmkvist from Sweden.
After the Olympics, Migiakis, who had also been the Greek featherweight champion eight times, ended his career as an active wrestler.
