The 47-year-old musician's mansion was hit by robbers in wee hours - at around 3 am, law enforcement sources told TMZ.
The perpetrators are believed to have got in through a window or door on an upper floor, as a ladder was found in the backyard.
Carey was not in house while the burglary was carried out; she is in New York.
The robbers, however, tripped a silent alarm and her security did not know about the break-in until about 6-7 am.
Carey is the latest celeb to have been become a victim of a high-profile burglary in and around the LA area, with Hilary Duff, Nick Young, Kendall Jenner, Kevin Hart, David Spade, Emmy Rossum among others in the list.