Emily Leatherman was taken into custody Sunday after Los Angeles County sheriff's deputies were called to Cusack's neighborhood, where a cab driver reported that a passenger didn't have enough money to pay for the ride to get there, sheriff's spokesman Steve Whitmore said Monday.
As the deputies were responding to the situation, they were flagged down by Cusack.
"He told them he recognized the woman in the cab and that she had been stalking him," Whitmore said.
He said deputies found evidence at the scene that led to the arrest, but he declined to elaborate, citing the investigation.
Leatherman was arrested for investigation of stalking, violating a restraining order and petty theft. She was being held on $150,000 bail.
Whitmore said the 33-year-old woman is "considered a transient in the Santa Monica area."
A call to Cusack's publicist wasn't immediately returned.
In July 2006, Cusack was granted a temporary restraining order stipulating that Leatherman stay at least 500 feet away from him, his home, his work, his car and offices or companies in which he does business.
In court papers, Cusack said Leatherman "is showing unusual interest by stalking, throwing long letters of interest over my fence in bags with rocks and screwdrivers inside, making unannounced visits to offices of people I work with in an attempt to meet with me and listing my address as her own during a recent arrest."
Leatherman has claimed she only sent Cusack two letters.