A lawyer by education, Niinistö was Minister of Finance from 1996 to 2003 and the National Coalition Party candidate in the 2006 presidential election. He served as the Speaker of the Parliament of Finland from 2007 to 2011 and has been the Honorary President of the European People’s Party (EPP) since 2002.
Niinistö was the National Coalition Party candidate in the 2012 presidential election, beating Pekka Haavisto of the Green League with 62.6% of the vote in the decisive second round. Niinistö assumed office on 1 March 2012, and is the first president from the National Coalition Party since Juho Kusti Paasikivi, who left office in 1956.
Niinistö served on the municipal council of Salo from 1977 to 1992 and was elected a Member of the Finnish Parliament (Eduskunta) from the district of Finland Proper in 1987. In 1994 he was chosen to lead the National Coalition Party as the party chairman and subsequently became Justice Minister in Prime Minister Paavo Lipponen‘s first cabinet in 1995.
Switching portfolios, Niinistö became Finance Minister in 1996, a place he held also in Lipponen’s second cabinet from 1999–2003. In both cabinets, the right-wing Niinistö was deputy to social democrat Lipponen, thus enabling the use of the term rainbow government in reference to Lipponen’s two consecutive cabinets. As Finance Minister, Niinistö was known for his strict fiscal policy as well as his hobby of roller skating. He was the first Finn to buy with euro cash on 1 January 2002. Niinistö was urged by his party to stand for president in the elections of 2000, but he refused. Niinistö announced his gradual retirement from politics in 2001, a course of action he has not completely followed to date. He was succeeded that year by Ville Itälä as party leader. Upon the end of his term as a cabinet minister in 2003, Niinistö went on to become vice-chairman of the Board of Directors at the European Investment Bank.
In March 2005, Niinistö announced his candidacy for the Finnish Presidency. He represented the National Coalition Party, challenging the incumbent President Tarja Halonen. He qualified for the second round runoff (as one of the top two candidates in the first round), held on 29 January 2006, but was defeated by Tarja Halonen. Total funds for Niinistö’s 2006 president campaign were circa 2,225,000 euros, including 492,864 euros and 717,191 euros contributions from the National Coalition Party. Financial declaration in 2006 was made more detailed in 2009 because of campaign finance controversies in Finland.
In 2006, Niinistö announced that he was standing again for the Finnish parliamentary election. He said, however, that he had no plans to take any high-ranking political job like the prime ministership in the future. He received 60,498 personal votes in the 2007 elections, which is a record number of votes for one candidate in a Finnish parliamentary election. It was about 50% more than the earlier record of Hertta Kuusinen. After the 2007 election, Niinistö decided to take the respected position of the Speaker of the Parliament. Niinistö is also the Honorary President of the European People’s Party (EPP), having successfully negotiated the merger of the European Democrat Union (EDU) into the EPP in 2002.
Niinistö is supportive of tough fiscal reforms to plug the country’s deficit and make sure it retains its triple-A credit rating.
Niinistö was the National Coalition Party candidate for a second time in the 2012 presidential election. With 37.0% of the vote, he won the first round of the election and faced off against Pekka Haavisto of the Green League in the decisive second round. He carried the second round with around 62.6% against Haavisto’s 37.4%. Niinistö’s margin of victory was larger than that of any previous directly elected president. He won a majority in 14 of the country’s 15 electoral districts. Niinistö’s election budget was circa 1.2 million euros.
Niinistö has pledged to establish a special task force aiming at preventing alienation among the young and expressed concern about the problems of sparsely populated rural areas. Niinistö stressed the significance of mutual understanding with the cabinet and Parliament. He gave an emotional speech in which he thanked not only those who backed him in the campaign, but also those who disagreed with him. Niinistö said that the differing views expressed should be taken into consideration in the work of the president.
Niinistö’s first wife, Marja-Leena Niinistö, died in a car accident in 1995. Niinistö married his second wife Jenni Haukio (born 1977) in January 2009.
While a cabinet minister, Niinistö, a widower, was romantically involved with MP Tanja Karpela, a former beauty queen and later Minister of Culture. Karpela’s Centre Party was in opposition and Niinistö was considered the second-most influential man in government. Under close press scrutiny ever since, in 2003 Karpela and Niinistö announced their engagement, which was however called off in 2004.
In Finland, Niinistö is also remembered as one of the survivors of the 2004 Indian Ocean earthquake. He escaped the ensuing tsunami by climbing up a utility pole with his son Matias in Khao Lak, Thailand.
Niinistö visited Russia as president in Feb 2013 to promote business (e.g. Shell, Cargotec, YIT). Niinistö address formally Putin (in German siezen). He discussed ice hockey and business but not the human rights issues or the actual military equipment selling to Syria and the transport through Finland.
Sauli Niinistö received €50,000 funds in the Finnish presidential election, 2006 from Ahti Vilppula company without giving required information. His company Helsingin Mekaanikontalo is registered in British Virgin Islands. In year 2009 media found out that Niinistö did not give data of election funds in time. Also center party Matti Vanhanen left €25,000 fund from Virgin Islands unreported. Virgin Islands is regarded as tax haven.
- Finland : Grand Cross of the Order of the White Rose of Finland with collar
- Finland : Grand Cross of the Order of the Lion of Finland
- Finland : Grand Cross of the Order of the Cross of Liberty
- Denmark : Knight of the Order of the Elephant (April 2013) 
- Greece : Order of the Phoenix
- Iceland : Grand Cross of the Order of the Falcon
- Italy : Order of Merit of the Italian Republic
- Lithuania : Grand Cross of the Order of Vytautas the Great with Golden Chain
- Netherlands : Order of Orange-Nassau
- Norway : Royal Norwegian Order of Merit
- Norway : Grand Cross of the Order of St. Olav (Oct. 2012)
- Sweden : Knight of the Royal Order of the Seraphim (2012)