[4] Paasikivi was born Johan Gustaf Hellsten (Finland Swedish pronunciation: [ˈjuhɑn ˈgʉstɑːf ˈhelːsteːn]) in 1870 at the smoke sauna of the Kulma-Seppälä house in the Huljala village of Koski Hl (today Hämeenkoski) in Päijänne Tavastia in Southern Finland, to Tamperean travelling merchant August Hellsten and his wife, Karolina Wilhelmina, née Selin.

His father had recognized his son's academic talent and enrolled him at a top elementary school in Hämeenlinna following brief attendance at Hollola.

[7] He entered the University of Helsinki in 1890, graduating in May 1892 with a Bachelor's degree in Russian language and literature,[8] a course of studies that proved useful in later life.

During his schooling, Paasikivi supported himself by working variously as a teacher, lecturer, court bailiff, and lawyer in private practice in Lahti.

He belonged, however, to the more complying Finnish Party, opposing radical and potentially counter-productive steps which could be perceived as aggressive by the Russians.

In 1914, after resigning his position at the Treasury, and also standing down as a member of Parliament, Paasikivi left public life and office.

After the 1917 February Revolution in Russia, Paasikivi was appointed to the committee that began formulating new legislation for a modernized Grand Duchy.

However, he was persuaded to accept the position of Envoy to Sweden, at the time regarded as Finland's most important foreign embassy post.

The threats from totalitarian regimes that had seized power in Germany and the Soviet Union made Finland increasingly isolated.

Since around the time of the failed Lapua coup, Paasikivi and Mannerheim had belonged to a close circle of conservative Finns discussing how Sweden's support could be obtained.

This didn't improve Paasikivi's reputation among the Swedish Social Democrats dominating the government, who were sufficiently suspicious due to his association with Finland's Monarchist orientation in 1918, and the failed Lapua coup in 1932.

When the war broke out, Paasikivi was asked to enter Risto Ryti’s cabinet as a minister without portfolio—in practice in the role of a distinguished political advisor.

He ended up in the cabinet's leading triumvirate together with Risto Ryti and Foreign Minister Väinö Tanner (chairman of the Social Democrats).

His main effort was to prove that Finland would present no threat to the Soviet Union, and that both countries would gain from confident peaceful relations.

Paasikivi concluded that, all the fine rhetoric aside, Finland had to adapt to superpower politics and sign treaties with the Soviet Union to avoid a worse fate.

Paasikivi's ability to speak some Russian helped his relations with the Soviet leaders; he did not have to use interpreters all the time, as his successor Kekkonen did.

As a lover of sports, and a former athlete and gymnast, Paasikivi had the great pleasure, during his second term of office, of opening the 1952 Summer Olympics held in Helsinki.

The President's speech was as follows:It gives me great pleasure to address a message of greeting to the young people of the world as they prepare for the fifteenth Olympic Games which are, once again, to be celebrated in a spirit worthy of the ideals of Baron de Coubertin.

This happy cooperation between young people of all countries will serve the great call of concord and peace among the nations of the world.

I am convinced that the Finnish people, loving sport as they do, will spare no effort to make the 1952 Olympic Games a complete success.

[16]By the end of Paasikivi's six-year second term, Finland had rid itself of the most urgent political problems resulting from the war.

The Karelian refugees had been resettled, the war reparations had been paid, rationing had ended, and in January 1956 the Soviet Union removed its troops from the Porkkala naval base near Helsinki.

His last-minute candidacy was based on a misunderstood message from some conservatives which made him believe that enough Agrarians and Social Democrats would support him.

In the 2019 Finnish television series Shadow Lines [fi] (Nyrkki), Paasikivi appears as a character with Urho Kekkonen.