Corrections spokeswoman Terry Thornton said Wednesday that guards found the phone Jan. 6 at Corcoran State Prison. This is the second time Manson has been caught with a phone, which violates prison rules.
Manson previously was caught with a phone in March 2009. He had been calling and texting people in California, Florida, New Jersey and British Columbia. At that time, he had 30 days tacked on to his sentence and he'll probably get more this time.
Manson is serving a life sentence for killings including the infamous murders of actress Sharon Tate and six others in Los Angeles in 1969.
Manson is technically eligible for parole, but it's doubtful he'll ever be released.
The Associated Press contributed to this report.