Bruce Willis' daughter shared the news with her over 400K Instagram followers on Friday ... as she wrote alongside a throwback video of herself and her A-list father, “Tell me you're autistic without telling me you're autistic."

In the resurfaced footage, Tallulah can be seen rubbing her dad's bald head over and over again as he gave a red-carpet interview. Tallulah's older sister Scout responded to the video by saying the actress is "stimming" in the clip.

For those who may not know ... stimming is defined as the repetitive performance of a certain physical movement -- and is a common behavior in autistic individuals.

This is the first time Tallulah has discussed her diagnosis, which she explained she found out about over the summer ... something she says changed her life.

This revelation comes a month after Tallulah gave a candid update regarding her recovery from an eating disorder. Tallulah first opened up about her struggles with anorexia back in May 2023.

Nine months later, Bruce's daughter with ex-wife Demi Moore confessed she was "romanticizing unhealthy times" and wanted to share the update in order to feel less alone. She encouraged herself and her followers to remember that it is ok to not have everything figured out.

In addition to Tallulah's health journey, the Willis family has been rallying around Bruce after his frontotemporal dementia diagnosis. Bruce's wife -- with whom he shares daughters Mabel and Evelyn -- said in September that it's unclear what the actor knows about his condition.