Kostadinov qualified for the Bulgarian squad in the men's shot put at the 2004 Summer Olympics in Athens. Earlier in the process, he eclipsed a B-standard entry mark of 20.02 metres from the European Cup Series in Plovdiv. Held inside the renowned Ancient Olympia Stadium, Kostadinov launched a satisfying 17.75-metre shot on his first attempt in the prelims. Upon receiving two marks short of his first throw, Kostadinov's effort was not enough to put him further to the final round, as he finished only in thirty-seventh out of 39 registered shot putters in the overall standings.