The Welsh will open their campaign against the Wallabies on November 4 - offering the Wallabies a chance to avenge yesterday's defeat - before hosting the Pacific Islands, Canada and New Zealand on consecutive weekends at the Millennium Stadium.
"We have agreed an extra match next year against Australia," said Welsh Rugby Union chief executive David Moffett.
"Australia is the extra match and will be on the first weekend of November. The Pacific Islands will be no easy opponents either.
"We have to keep playing these teams. The significant thing about Australia is that they are in our World Cup group."
Over 300,000 fans streamed through the gates to watch Wales against New Zealand, Fiji, South Africa and Australia this November.
The schedule for 2006 is not ideal for coach Mike Ruddock, who will have to release his key players back to club duty for one of the four weekends.
This year Wales fielded a weakened team against Fiji and Ruddock admitted it disrupted their preparations.
Given he is likely to release players for the Canada game, Wales will have limited preparation time ahead of the New Zealand clash.
But Moffett said: "That is what happens in the World Cup. You will have a hard game then an easier game. You have to get on with it and we certainly did that this year.
"We were poor against New Zealand, ordinary against Fiji. We improved last week and certainly improved again this week to beat Australia.
"That is a significant result because Australia did not have a poor team out there."