In April 2006 he announced that he would play for the Western Force Super Rugby team, in the 2007 Super 14 season. He was included in the Wallabies 2006 mid-year rugby tests squad, but was ruled out with an injury. However he recovered in time for the 2006 Tri Nations Series. He came off the bench in the first game in the series. In 2007, Giteau was selected for the Wallabies 2007 Rugby World Cup and 2008 squad and was first choice No. 12. He also had gained 40 test points, putting him in the top scorer's list in the competition. Giteau took injuries into the match, and the Wallabies lost in the quarter-final to England 10–12. Following Rugby World Cup, Giteau played fly-half for the Barbarians against Rugby World Cup winnersSouth Africa. Giteau scored a try, and the Barbarians won 22–5.
2008
In 2008, new Wallabies coach Robbie Deans selected Giteau as Australia's new fly-half, following the retirement of Stephen Larkham. Giteau played fly-half against Ireland and France in the mid year test. In the 2008 Tri Nations Series, Giteau played in all six games. He played against the All Blacks winning 34–22 at the ANZ Stadium in Sydney, and against South Africa winning 27–15 at Kings Park Stadium in Durban. He was also a part of the Wallabies' record loss that following week to South Africa 53–8.
Super Rugby
Giteau played for the Western Force for 2007–09. In 2007 the Force finished seventh, and recorded their first home win. In 2010 Giteau returned to Canberra and the Brumbies, where he played for 2010 and 2011.
Move to France
During the 2011 Super Rugby season, Giteau signed with the French club Toulon, a move that would take effect after the 2011 Rugby World Cup. Despite not being selected for the Australian World Cup squad, he could not join Toulon until mid-November, as he was still under contract with the Australian Rugby Union through the World Cup. In May 2013 he started as Toulon won the 2013 Heineken Cup Final by 16–15 against Clermont Auvergne. He has won 3 European titles with Toulon starting all 3. In 2015 they wrote history for winning 3 successive European titles,. He also won the top14 orange in 2014.
2015
In 2015, national coach Michael Cheika made negotiations with the Australian Rugby Union to allow players with 60 caps or more eligible to represent the Wallabies despite not playing in the Super Rugby. Giteau played against the Springboks winning 24–20 at the Suncorp Stadium, and against the All Blacks 27–19 at the ANZ Stadium. Giteau was selected in the Wallabies 31 Man squad to represent in the 2015 Rugby World Cup. In October, during the 2015 Rugby World Cup, Giteau scored his 30th International try for the Wallabies as part of their win against England, knocking them out of the tournament. Giteau was a key player for the Wallabies to reach the Rugby World Cup final, but his World Cup dream was short lasting as Matt copped a head knock in the opening stages of the match and ruled him out of the match, the Wallabies lost to the All Blacks 17-34
Move to Japan
In March 2017, Giteau announced that he would spend his last season with Toulon as a player-coach. On 15 May 2017, Giteau confirmed his move to Japan with Suntory Sungoliath in the Top League next season.