She started training in gymnastics in 1980 at age eight at the Deriugins School, coached by the mother/daughter combination of Albina and Irina Deriugina.

At age 14, she became the Soviet junior champion and, shortly after, collected three medals at a European championships: a gold for the Rope, a silver for the Hoop and a bronze for the Ribbon.

At the 1988 European Championships in Helsinki, Finland, Tymoshenko shared the All-Around title with two Bulgarians, Elizabeth Koleva and Adriana Dunavska.

She would grab her second European title in 1990, but spent the rest of the year struggling against the steadily rising Oksana Skaldina.

Although the Ukrainian Federation tried to persuade her to continue after the 1992 Olympics, Timoshenko opted to retire from the sport at the age of 20.