Sergiyenko was the European Junior champion in 1983 and won the bronze medal at the 1991 Summer Universiade. After representing the Unified Team at the 1992 Summer Olympics, he won the gold medal at the 1992 IAAF World Cup. His final international appearance came at the 1993 IAAF World Indoor Championships. He was a two-time Ukrainian national champion – being the first man to take the high jump title after the country's independence.