Louis Tomlinson has given $10,000 (£7,200) to a nine-year-old fan with cerebral palsy.
Rylee Sanford lives in Georgia, USA, and has a very rare brain malformation called bilateral close-lipped schizencephaly.
The condition causes her to have cerebral palsy and means that she can't walk without assistance.
Rylee's family are trying to raise $15,000 (£11,000) to make her house more accessible.
They say the money is to "help her reach her full potential and get her all the help she needs".
"The home modifications we need are a walk-in shower, widened doorways and a ramp added to our porch.
"Our next goal would be stem cell treatments as there have been a lot of great results.
"However, insurance will not cover most of this, and it is pretty expensive."
They go on to describe her as "sassy" and "a true warrior".
Her sister tweeted saying Rylee wanted to model like Gigi Hadid.
Relatives also listed some things she likes - including Louis and his ex-One Direction band mates.
Louis shared a picture of her and a link to the page on Twitter which gained extra interest in the cause.
The family is often getting in touch with the celebrities she loves and Louis is not the first of the One Direction boys to notice Rylee.
Early in 2017 Zayn retweeted a post from Rylee's older sister MaKayley, after she posted a video of Rylee listening to Zayn's new song in the car.
Speaking to Newsbeat, MaKayley expressed gratitude for the coverage the story has had.
And in a post on the fundraising page, Rylee's mum Lisa thanked fans for their generous donations.