Fieger, 53, had two brain tumors removed during the operation at Cedars-Sinai Medical Center, publicist Guy McCain said. There were no details about the tumors.
Dr. John Yu said the surgery was successful and Fieger was expected to have a full recovery, McCain said in a statement.
The Knack's upcoming concert tour was postponed, McCain said. The tour had included stops Aug. 11 at the Corbin Music Festival in Corbin, Ky., and Sept. 2 at the Oregon State Fair in Salem, Ore.
The Knack was formed in 1978 and a year later hit it big with "My Sharona." The group's debut album "Get the Knack" sold 6 million copies, followed by a second album "... But the Little Girls Understand," which sold 2 million.
Singer-songwriter Fieger said "My Sharona" was inspired by a girlfriend of four years.
"I had never met a girl like her — ever," he told The Associated Press in a 1994 interview. "She induced madness. She was a very powerful presence. She had an insouciance that wouldn't quit. She was very self-assured. ... She also had an overpowering scent, and it drove me crazy."
Fieger was frank about a period of drug abuse during which he said he "should have died for a number of years."
"I have this feeling that human beings are allowed so much alcohol in their lives and so much drugs, and I just used mine up — and a couple of other people's, too," he said.