Her fiancée, Tila Tequila announced the death on her Twitter on Monday night.
"Everyone please pray 4 my Wifey Casey Johnson. She has passed away," Tila wrote. "Thank u for all ur love and support but I will be offline to be w family."
Los Angeles Police said the body of the 30-year-old socialite was discovered inside a home following an ambulance call just before noon on Monday.
Johnson had a troubled past, including a history of drug problems and has failed at rehab several times.
She was arrested in November for grand theft involving a former girlfriend, Jasmine Lennard.
The Jets issued a statement on Monday night:
"The Johnson family is mourning its tragic loss, and asks for privacy during this very difficult time."
LAPD said they believe her death was from natural causes. There is no evidence of foul play.
The coroner's office will perform toxicology tests to determine the exact cause of death.