Paul Pelosi, the husband of House Speaker Nancy Pelosi, was "violently assaulted" after a break-in at the couple's California home early on Friday, her office said in a statement.
"The assailant is in custody and the motivation for the attack is under investigation," the statement said.
"Mr. Pelosi was taken to the hospital, where he is receiving excellent medical care and is expected to make a full recovery."
The Democratic speaker of the US House of Representatives, who is second in line to the presidency, was not at home at the time of the early morning assault.
The circumstances of the attack were unclear, including how the intruder got into the home.
The assault comes less than two weeks before midterm elections in which control of the House and the Senate is at stake.
Paul Pelosi, 82, who owns a San Francisco-based real estate and venture capital firm, was convicted of a misdemeanor charge of driving under the influence of alcohol after becoming involved in an auto accident in May.
He was sentenced to five days in jail in Napa County, California.
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