Renee Cuela, 44, who pleaded "no contest" to the charges in February, must pay restitution to victim of $64,000, plus $560 in fines. She was sentenced by Judge Susan Etezadi of the San Mateo County Superior Court.
The theft occurred in August 2008.
Her prison time will be reduced by the nine days she spent in county jail, said Chief Deputy District Attorney Steve Wagstaffe in a report.
Ms. Cuela, who is now in custody, will serve 50 percent of her sentence since this conviction does not involve registering as a sex offender, nor does it qualify as a strike under the three-strikes law, Assistant District Attorney Karen Guidotti said.
The missing jewelry came to light when the residents of the Selby Lane home returned from a trip to discover what initially seemed like a burglary, but there were no signs of forced entry and the house was unlocked, prosecutors said.
The stolen jewelry included a pair of diamond earrings valued at $60,000, two wedding rings and a diamond necklace.
The nanny employed at the residence told authorities that Ms. Cuela had taken her shopping one afternoon and "constantly acted like she wanted to keep (the) nanny away from the house," prosecutors said.
Ms. Cuela also stole about $10,000 over several months through the use of the nanny's debit card, prosecutors added.
Saying she could not face either the family or the nanny, Ms. Cuela left them letters in May 2009 admitting that she had stolen from them, prosecutors said.
Ms. Cuela later admitted in an interview with police that she had acted in concert with her boyfriend and had pawned much of the stolen jewelry, prosecutors said. She also apologized for the thefts.