International Airlines Group has signed a memorandum of understanding with Airbus for eight A330-300s plus options on a further eight.
The aircraft will be used to replace subsidiary Iberia's A340 fleet, says an Iberia spokesman.
Deliveries are scheduled between this autumn and spring 2014.
IAG has yet to select an engine for the aircraft.
IAG chief executive Willie Walsh said last month that replacing Iberia's A340s would be a priority ahead of a broader long-haul fleet renewal programme that will also encompass the needs of British Airways.
BA and Iberia jointly operate more than 160 widebodies, with Iberia's fleet consisting of 18 A340-300s and 17 A340-600s and BA operating 57 Boeing 747-400s, 21 767-300ERs and 49 777s.