In January 2018 Nassar was sentenced to up to 175 years after nearly 160 women accused him of sexual abuse.
Biles, 21, then told her own story of how she was one of those victims.
"It was very hard but I figured out that if I can tell my story then it might encourage other people to tell theirs," she said.
Biles, who won four gold medals and a bronze at the Rio Olympics in 2016, said she wanted to speak out about the reaction to her revelation and her responsibility as a role model.