He has been President of French Polynesia (président de la Polynésie française), an overseas collectivity of France, on five occasions: in 2004, from 2005 to 2006, from 2007 to 2008, in 2009, and from 2011 to 2013 and mayor of Faa'a since 1983.

He first served as the President of French Polynesia (président de la Polynésie française) from June 15, 2004 until his Government lost a no-confidence motion on October 8, 2004.

On October 8, 2004, his government was censured and ousted by the Parliament, the Assembly of French Polynesia (Assemblée de la Polynésie française) by a vote of 29 to 28.

Temaru lost a vote of no confidence on 13 December 2006, after months of protests against the high cost of living in French Polynesia.

[5] It was under Temaru's presidency that French Polynesia became, in November 2011, a founding member of the Polynesian Leaders Group, a regional grouping intended to cooperate on a variety of issues including culture and language, education, responses to climate change, and trade and investment.

[12][13] An early political influence was Jean-Marie Tjibaou, philosopher and former leader of the Kanak Socialist National Liberation Front (FLNKS), who was assassinated in New Caledonia in 1989.

Temaru's coalition government program in 2004 included the gradual increase of the minimum wage to 150.000 Fcfp, work days that don’t start before 9 am, an improvement of social services, political decentralisation, educational reform, and a revision of the new autonomy statute after French Polynesia was declared a French Overseas Country (pays d'outre-mer) in March 2004.

In 2007, Temaru was found guilty of "racial discrimination" by the criminal court of Papeete for having referred to the European people living in French Polynesia as "trash", "waste".

[15] In September 2019, Oscar Temaru was convicted of 'unlawful taking of interests' (prise illégale d'intérêts) by the criminal court of Papeete for exercising undue influence as mayor of Faaa.

[18] Oscar Temaru announced his new presidential cabinet on September 19, 2007, shortly after his election as President of French Polynesia.