At the time of the searches, Shandling was involved in a lawsuit in which he accused former manager and now Paramount studio head Brad Grey of taking excess commissions and fees from the HBO series "The Larry Sanders Show."
Attorney Bert Fields, who represented Grey, called the lawsuit "sheer lunacy" when it was filed in 1998.
On Thursday, Shandling leafed through a printout of the background checks that also included names of his friends and associates.
"This bothers me as much as the first time I saw this," the 58-year-old said. "It's a creepy feeling."
Prosecutors said Shandling was among the victims of a racketeering scheme headed by investigator Anthony Pellicano that dug up dirt on celebrities and other prominent Hollywood clients for use in legal and other disputes.
Pellicano, 63, and four co-defendants have pleaded not guilty to various charges. Pellicano is acting as his own lawyer.
For about 45 minutes, Shandling chronicled his falling out with Grey after hiring him as his manager in the early 1980s.
After learning that Fields would represent Grey, Shandling recalled a conversation he had years earlier with Grey.
Grey said, "'with Bert Fields, you get Anthony Pellicano,"' Shandling said. "I didn't quite know what he meant then."
Shandling later had a security consultant examine his phone for any wiretaps but none was found, Shandling testified.
In a statement Thursday, Grey said he was "extremely saddened" by Shandling's recollection of events, adding their friendship was overtaken by a legal process directed by lawyers.
Shandling "remains one of the most talented people I have known and I wish him only the best," Grey said.
Prosecutors believe Pellicano bribed police officers, including LAPD Sgt. Mark Arneson, his co-defendant, to run names of his clients' rivals through databases.
During cross-examination by Arneson's attorney, Shandling said he didn't know if any of the information had been used against him.
The lawsuit against Grey was settled in July 1999 for a reported $10 million.
Both Grey and Fields have denied knowing of Pellicano's tactics and have not been charged in the case. Their names appear on the prosecution witness list, but it was unclear if either would testify.
In a lighter moment, Shandling and U.S. District Judge Dale Fischer drew laughs in the courtroom when he first took the stand and was asked by prosecutor what he did for a living.
"I'm a comedian" Shandling replied.
"Not today, sir," Fischer cracked.
