Niall Horan says abusive messages sent to his phone have kept him awake at night.
"For the last two weeks I've been receiving messages off a group of fans," the singer tweeted.
He added: "They have drowned my phone in messages, keeping me awake at night."
The One Direction star also revealed that his nephew and other family members had been mentioned.
After posting his comments Niall received positive messages from fans all over the world.
The 22-year-old reassured them that he was able to deal with the negative attention.
Vlogger and YouTube star Alfie Deyes replied to one of Niall's tweets and thanked him for speaking out.
Niall is the latest celebrity to speak out against online abuse.
Cheryl Fernandez-Versini, diver Tom Daley and Jessie J have previously called for more to be done to stop it.
With One Direction still on hiatus Niall has used his free time to set up a sports management company.
Niall, who's worth a reported £20m, may also be thinking about a future solo career.
One Direction haven't revealed exactly when they'll be returning but in several interviews have insisted the group have not split for good.