In August 2017, Biles announced on Instagram that she was dating fellow gymnast Stacey Ervin Jr.[156] They split after three years of dating.[157][158] She has a French bulldog named Lilo.[159]

In August 2020, her relationship with professional American football player Jonathan Owens became "Instagram-official".[160]

On January 18, 2018, Biles released a statement on Twitter confirming that former USA Gymnastics physician Larry Nassar had sexually assaulted her. She also named USA Gymnastics for having an alleged role in allowing the abuse to occur, and for subsequently covering it up.[161] She did not attend court hearings held from January 16 to 24, 2018, citing that she "wasn't emotionally ready to face Larry Nassar again."[162][163] In May 2018, it was announced that Biles and the other survivors would be awarded the Arthur Ashe Courage Award. At the 2018 U.S. National Championships, Biles designed and wore a teal leotard that she stated was meant to honor the survivors of Nassar's abuse, as a statement of unification.[164]

In September 2016, Biles opened up about having ADHD (Attention Deficit Hyperactivity Disorder) after her medical records were leaked online, revealing that she had been taking Ritalin, used to treat the condition, during the Olympics. Having been diagnosed as a child, she had previously disclosed her condition to the World Anti-Doping Agency and obtained a medical exemption, allowing her to take her medication during competitions. In her statement, she said that ADHD is "nothing to be ashamed of and nothing that I'm afraid to let people know."[165][166][167]