The former Partridge Family star was rushed to a Florida hospital on Wednesday, and has been there since, a rep for Cassidy tells ET.
"His organs are failing," the rep reveals. "He is currently conscious and surrounded by family."
Cassidy, 67, has also been suffering with dementia, after being diagnosed with the disease over two years ago. The performer initially kept the disease a secret, but went public after concert footage showed him struggling to recall lyrics.
In an interview with Dr. Phil in February, Cassidy opened up about his diagnosis and his fears following his mother, actress Evelyn Ward's, death of Alzheimer's-related dementia in 2012.
"[I fear being] in a place my mother was the last two years of her life, where I would completely disappear," he confessed. "I'd just be a burden to caretakers and couldn't walk, couldn't talk, couldn't sing, couldn't play. That's kind of my greatest fear."