Bre-Andria Rousell of New Orleans, Louisiana, US, claimed to have been watching a YouTube video when Momo attempted to befriend her.
The viral craze sees a creepy female figure with twisted features encouraging teenagers to self-harm and even take their own lives.
It first started as a sick WhatsApp “suicide” game, before reportedly spreading to YouTube and other social media sites.
Horrified mum Brittany Rousell, 27, shared a video of the worrying conversation when her daughter detailed how the disturbing challenge can target you.
In the video, the youngster tells her mum: “Momo is an app and you can call and text her.
“When you call or text her, she’ll answer and then hang up and it starts getting freaky.
“If you text her asking if you can be friends, she’ll say ‘yes, we can be best friends’.
“She’ll send you her address and if you go to her house, she’ll actually kill you.
“And I don’t want that happening to me.”
The six-year-old issues a stark warning to others: “Make sure Y’all stay safe, ok?”
Brittany is left clueless by her young daughter’s traumatising detailing and seeks to dig further.
Bre-Andria further adds: “She’ll be in your dreams, or she’ll kill you.”
“She’ll ring you and if you don’t pick up, the lights will cut off and it’ll get really really freaky.
“I don’t do that app, because I don’t want to get killed.”
When detailing what Momo looks like to her mum, the girl can be seen freaked out.
The mum-of-three shared the video to raise awareness about the potentially fatal challenge which encourages youngsters to harm themselves.
Since uploading the video online a day ago, hundreds of people have flooded in to watch the concerning parental moment.
“This is so scary, people are sick,” one parent claimed.
“Thanks for the heads up,” another added.
YouTube said it had not received any evidence of the challenge on its site.
It comes after a five-year-old chopped her hair off after being brainwashed by the character.