The California Highway Patrol said Mr Pelosi had been attempting to cross State Route-29 when his car was struck by a 48-year-old man driving a Jeep.
California law states drivers cannot operate a vehicle if their blood alcohol level is more than 0.08%. Authorities have not said what Mr Pelosi's level was.
Mrs Pelosi was delivering an address at Brown University when the incident happened.
Her spokesman released a statement saying she would not be commenting on the "private matter".
Paul Pelosi has not yet commented on his arrest.