[2] In 2003, Zuzana Hejnová competed at the 2003 World Youth Championships in Athletics at Sherbrooke, Canada and won the gold medal in the 400-metre hurdles with a time of 57.54.

[4] At the 2012 London Olympics, Hejnová won originally the bronze medal for the women's 400 m hurdles, behind the winner, Russia's Natalya Antyukh, and Lashinda Demus of the United States.

In December, it was announced that she had been stripped of her title and Demus would be upgraded to gold in her place, with Hejnová then second.

She secured maximum points for Czech Republic in the European Team Championships First League in Dublin by winning the 400 m in 51.90 seconds.

Despite winning her semi-final,[9] Hejnová came fourth in the 400-metre hurdles at the 2016 Olympic Games in Rio de Janeiro.

[10] She threatened to sue Czech Post for 1 million koruna over the use of her likeness on a stamp celebrating the 2016 Olympic Games.

[11] The Court of Appeal found in favour of Hejnová, leading to Czech Post paying her an undisclosed settlement.