Asō, a Catholic, was born in Iizuka in Fukuoka Prefecture on 20 September 1940. His father, Takakichi Asō, was the chairman of the Aso Cement Company and a close associate of Prime Minister Kakuei Tanaka; his mother Kazuko Asō was Prime Minister Shigeru Yoshida’s daughter. Tarō is also a great-great-grandson of Ōkubo Toshimichi, and his wife, Chikako, is the third daughter of Prime Minister Zenkō Suzuki. His younger sister, Nobuko, Princess Tomohito of Mikasa, is a cousin-in-law of Emperor Emeritus Akihito.

In mid-2008 Asō conceded that his family’s coal mine, Aso Mining Company, was alleged to have forced Allied prisoners of war to work in the mines in 1945 without pay. Western media reported that 300 prisoners, including 197 Australians, 101 British, and two Dutch, worked in the mine. Two of the Australians, John Watson and Leslie Edgar George Wilkie, died while working in the Aso mine. In addition, 10,000 Korean conscripts worked in the mine between 1939 and 1945 under severe, brutal conditions in which many of them died or were injured while receiving little pay. The company, now known as the Aso Group, is run by Asō’s younger brother. Asō’s wife serves on its board of directors. Asō headed the company in the 1970s before going into politics.

Asō spent two years working for a diamond mining operation in Sierra Leone before civil unrest forced him to return to Japan. Then he joined his father’s company in 1966, and served as president of the Aso Mining Company from 1973 to 1979. Working for the company, he lived in Brazil during the 1960s and became fluent in Portuguese. He was also a member of the Japanese shooting team at the 1976 Summer Olympics in Montreal and President of the Japan Junior Chamber in 1978.

In 2001, as economics minister, he was quoted as saying he wanted to make Japan a country where “rich Jews” would like to live.

In 2001, Asō, along with Hiromu Nonaka, was among the LDP’s chief candidates to succeed Yoshirō Mori as prime minister of Japan. During a meeting of LDP leaders at which Nonaka was not present, Asō reportedly told the assembled group, “We are not going to let someone from the buraku become the prime minister, are we?” Asō’s remark was apparently a reference to Nonaka’s burakumin, a social minority group in Japan, heritage.

He joined the Cabinet of Jun’ichirō Koizumi in 2003 as Minister of Internal Affairs and Communications. On 31 October 2005, he became Minister for Foreign Affairs. There has been some speculation that his position in the Cabinet was due to his membership in the Kōno Group, an LDP caucus led by pro-Chinese lawmaker Yōhei Kōno: by appointing Asō as Minister for Foreign Affairs, Koizumi may have been attempting to “rein in” Kōno’s statements critical of Japanese foreign policy.

Asō has been a fan of manga since childhood. He had his family send manga magazines from Japan while he was studying at Stanford University. In 2003, he described reading about 10 or 20 manga magazines every week (making up only part of Asō’s voracious reading) and talked about his impression of various manga extemporaneously. In 2007, as Minister for Foreign Affairs, he established the International Manga Award for non-Japanese manga artists.

On 15 October 2005, during the opening ceremony of the Kyushu National Museum which also displays how other Asian cultures have influenced Japanese cultural heritage, he praised Japan for having “one culture, one civilization, one language, and one ethnic group”, and stated that it was the only such country in the world. This statement sparked controversy for what critics described as invoking Japan’s imperialist and racist past.

On 21 December 2005, he said China was “a neighbour with one billion people equipped with nuclear bombs and has expanded its military outlays by double digits for 17 years in a row, and it is unclear as to what this is being used for. It is beginning to be a considerable threat”. On 28 January 2006, he called for the emperor to visit the controversial Yasukuni shrine. He later backtracked on the comment, but stated that he hoped such a visit would be possible in the future.

Nonaka subsequently withdrew as a candidate. Asō eventually lost the appointment to Jun’ichirō Koizumi. Asō’s comment about Nonaka’s heritage was revealed in 2005. Asō denied that he had made the statement, but Hisaoki Kamei, who was present at the 2001 meeting, stated in January 2009 that he had heard Asō say something, “to that effect”. Nonaka said that he would “never forgive” Asō for the comment and went on to state that Asō was a “misery” to Japan.

Asō was one of the final candidates to replace Koizumi as prime minister in 2006, but lost the internal party election to Shinzo Abe by a wide margin. Both Abe and Asō are conservative on foreign policy issues and have taken confrontational stances towards some East Asian nations, particularly North Korea and, to a lesser extent, the People’s Republic of China. Abe was considered a more “moderate” politician than the more “hard-line” Asō, and led Asō in opinion polling within Japan. Asō’s views on multilateralism are suggested in a 2006 speech, “Arc of Freedom and Prosperity: Japan’s Expanding Diplomatic Horizons”.

Kyodo News reported that he had said on 4 February 2006, “our predecessors did a good thing” regarding compulsory education implemented during Japan’s colonization of Taiwan.

Mainichi Daily News reported that on 9 March 2006 he referred to Taiwan as a “law-abiding country”, which drew strong protest from Beijing, which considers the island a part of China.

On 1 August 2008, Fukuda appointed Asō as Secretary-General of LDP, a move that solidified Asō’s position as the number two man in the party.

Unexpectedly on 1 September 2008, Fukuda announced his resignation as Prime Minister. Five LDP members including Asō ran for new party President to succeed Fukuda. On 21 September, one day before votes of Diet party members, Asō reportedly told a crowd of supporters outside Tokyo: “The greatest concern right now is the economy.” “America is facing a financial crisis … we must not allow that to bring us down as well.” Finally on 22 September, Asō did win. He was elected as President of LDP with 351 of 525 votes (217 from 384 Diet party members, 134 from 47 prefecture branches); Kaoru Yosano, Yuriko Koike, Nobuteru Ishihara, Shigeru Ishiba got 66, 46, 37, 25 votes respectively.

On 23 September 2008, Akahata, the daily newspaper published by Japanese Communist Party released a compiled list of these and other statements as the front-page article criticizing Asō. This compilation as well as similar lists of blunders have been frequently cited in the Japanese media.

Acting on a request from Yukihisa Fujita, the Foreign Ministry investigated and announced on 18 December 2008 that Aso Mining had, in fact, used 300 Allied POWs at its mine during World War II. The ministry confirmed that two Australians had died while working at the mine, but declined to release their names or causes of deaths for “privacy reasons”. Said Fujita, “Prisoner policy is important in many ways for diplomacy, and it is a major problem that the issue has been neglected for so long.” Asō has not responded to requests from former laborers to apologize for the way they were treated by his family’s company.

The Japanese media noted in November 2008 that Asō often mispronounced or incorrectly read kanji words written in his speeches, even though many of the words are commonly used in Japanese. Asō spoke of the speaking errors to reporters on 12 November 2008 saying, “Those were just reading errors, just mistakes.” Asō’s tendency for malapropisms has led comparisons to George W. Bush, and the use of his name, “Tarō” as a schoolyard taunt for unintelligent children.

In October 2008, the Japanese media reported that Asō dined-out or drank in restaurants and bars in luxury hotels almost nightly. When asked about it, Asō stated, “I won’t change my style. Luckily I have my money and can afford it.” Asō added that if he went anywhere else, he would have to be accompanied by security guards which would cause trouble.

According to the Asahi Shimbun, Asō dined-out or drank at bars 32 times in September 2008, mainly at exclusive hotels. Asō’s predecessor, Yasuo Fukuda, dined-out only seven times in his first month in office. Both of the LDP’s opposition parties have called Asō’s frequent outings inappropriate. Asō’s Chief Cabinet Secretary, Jun Matsumoto, commented on the issue by saying that Asō’s frequent trips to restaurants, “is his lifestyle and philosophy, and I am not in a position to express my opinion. If only there were more appropriate places when considering security issues and not causing trouble for other customers.”

Prime Minister Asō flew to Washington to meet with United States President Barack Obama in February 2009. He was the first foreign leader to visit the Obama White House; however, reports suggested that the new administration was interested less in giving Asō a political boost than in sending a message that Japan continues to be an important ally and partner – a low-risk, high-payoff gesture for both Asō and Obama.

After his election as prime minister Asō was expected to dissolve the lower house to clear the way for a general election. But he repeatedly stressed the need for a functioning government to face the economic crisis and ruled out an early election. Only after passage of the extra budget for fiscal 2009 in May and facing internal pressure from the LDP after a series of defeats in regional elections – most notably the Tokyo prefectural election on 12 July – he decided to announce a general election for 30 August 2009. He dissolved the House of Representatives on 21 July 2009. The LDP lost by a landslide to the Democratic Party of Japan, in the face of record levels of post-war unemployment. Accepting responsibility for the worst (and second-only) defeat of a sitting government in modern Japanese history, Asō immediately resigned as LDP president.

Yahoo! News reported that he had said on 9 January 2009, “To work is good. It’s completely different thinking from the Old Testament.”

When Shinzo Abe returned to the Prime Minister’s office in 2012, Aso is appointed Deputy Prime Minister and Minister of Finance. He is the first former Japanese Prime Minister to subsequently serve as Deputy Prime Minister.

While speaking at a meeting of the National Council on Social Security Reform, in 2013, Asō referred to patients suffering from serious illness as “tube persons” and remarked that they should be “allowed to die quickly” if they desired it. “Heaven forbid I should be kept alive if I want to die”, he is quoted as saying. “You cannot sleep well when you think it’s all paid by the government. This won’t be solved unless you let them hurry up and die.”

In 2014, while campaigning in Sapporo for the general election, Asō said that rising social welfare costs were not solely due to an aging population. He said, “There are many people who are creating the image that (the increasing number of) elderly people is bad, but more problematic is people who don’t give birth”. The comment was labeled as insensitive to those who are not able to have children for biological or economic reasons.

The Guardian reported on 30 August 2017, that he said, “Hitler, who killed millions of people, was no good even if his motive was right.” He later retracted the remarks.

According to The Japan Times, Asō “raised eyebrows” in June 2018 when he stated that the large support towards the LDP among voters under 35 in the 2017 general election was due to that demographic being less inclined than older Japanese to read newspapers, which had been critical of Abe’s handling of cronyism scandals.

In May 2018, Asō downplayed alleged sexual harassment charges against his ministry’s top bureaucrat by saying that “there is no such thing as a sexual harassment charge.” When asked to comment on a formal complaint submitted to his ministry on the alleged sexual harassment, Asō remarked that his “only thought was that it would have been easier to read if they used a bigger font.”