O'Connor posted the video on her Facebook page on August 3, but it started to get more attention in the last few days after fans started sharing it. It has racked up nearly 900,000 views and more than 5,800 shares on Facebook as of Tuesday morning.
In it, the "Nothing Compares 2 U" singer is seen crying in a motel room and lamenting that her family has abandoned her in the wake of mental health issues.
"People who suffer from mental illness are the most vulnerable people on Earth," O'Connor said. "You've got to take care of us. We're not like everybody."
Using the hashtag #OneOfMillions, the 50-year-old performer said it was her hope "that this video is somehow helpful."
"Not actually to me but the fact that I know that I'm only one of millions of millions of millions of people who are just like me actually who don't have necessarily the resources that I have in my heart or my purse for that matter," she said.
During the 12-minute long video, O'Connor said she was suicidal and feels like she is being punished for having mental illness. The only support she has, she said, is her psychiatrist and her doctor.
"Suddenly, all the people who are supposed to be loving you or taking care of you treat you like s***" she said. "If it was me, I'd be gone straight away back to my mom."
It's not the first time O'Connor's social media postings has caused alarm.
In 2015 she posted on her Facebook page that she had overdosed
in the wake of a custody battle involving her youngest son and his father, Irish musician Donal Lunny. Police later said they had located O'Connor and she was "safe and sound."
The following year, O'Connor was reported missing in Chicago when she did not return from a bike ride, but police found her a day later.
In this latest incident, O'Connor followed up the Facebook video with a post the next day that stated the address of a South Hackensack Travelodge motel in New Jersey.
But NorthJersey.com reported that
the establishment has no record of O'Connor staying there.
Singer Annie Lenox expressed concern for O'Connor in her own Facebook statement that was posted on Tuesday.
"I realise that Sinead has some serious mental health issues, but she appears to be completely out on a limb and I'm concerned for her safety," Lenox wrote. "Are there no close friends or family who could be with her to give her some loving support? It's terrible to see her in such a vulnerable state."
A posting on O'Connor's page post on Tuesday assured fans she was fine.
"Hi everybody, I am posting at Sinead's request, to let everyone who loves her know she is safe, and she is not suicidal," the posting said. "She is surrounded by love and receiving the best of care. She asked for this to be posted knowing you are concerned for her."
CNN has reached out to O'Connor's representatives for comment.