The law is headed to Gov. Jerry Brown's desk after winning approval in the Legislature. The Senate unanimously approved Assembly amendments to SB26 by Democratic Sen. Alex Padilla of Los Angeles on Thursday.
It would make it a misdemeanor to smuggle cellphones to California inmates.
Thousands of prisoners, including Charles Manson, have been caught with smuggled phones. The California Corrections Department confiscated more than 2,000 from inmates in the first two months of 2011 alone.
The law's supporters say inmates use the cell phones to order murders, organize crime deals and further terrorize victims.
The Associated Press contributed to this report.