Born in 1835 in Inokuchi village, Aki District, Tosa Province, into the house of a jige-ronin — a family that had half-peasant, half-samurai status, its ancestors having sold their samurai rank. From an early age he applied himself to study, and in Edo sat under Asaka Gonsai. After returning home he was spotted by Tosa's chief councilor Yoshida Toyo and put in charge of trade at the Nagasaki branch of the domain's Kaiseikan. In 1870 he took over the domain's shipping department and founded Tsukumo Shokai; in 1873 he renamed it Mitsubishi Shokai and made it his own enterprise. As a government-appointed shipper, he won enormous profits from military transport during the Taiwan Expedition of 1874, and in 1875, with government subsidies, established the Mitsubishi Steamship Company. He eliminated his rivals — the Japan Mail Steamship Company and the Kyodo Un'yu — and held a monopoly of Japanese shipping. He then expanded into mining (the Takashima coal mine and Sado gold mine), shipbuilding (the Nagasaki Shipyard), and finance. In 1885 he died of stomach cancer at fifty. Under his brother Yanosuke, his eldest son Hisaya, and his nephew Koyata, the Mitsubishi grew into one of Japan's largest zaibatsu.

A 'man of the sea' combining indomitable fighting spirit with coldly calculating business judgment. The backbone of a Tosa country samurai had him defiantly challenging the Edo-era caste system and vested interests. 'My ships are my castle,' he said, burning with obsession for the shipping trade, and as a political merchant he made the fullest use of government backing — an operator of iron will. On the other side, he was warm in feeling to family and fellow-countrymen, showing the breadth to entrust his enterprises to his brother and nephew.

The Mitsubishi that Yataro built was dismantled after the war by GHQ, yet in the form of Mitsubishi Heavy Industries, Mitsubishi Corporation, MUFG Bank, Mitsubishi Electric, Kirin Brewery, and others it continues to make up a core of the modern Japanese economy. The Nagasaki Shipyard, which built the battleship Musashi, stood at the summit of Japanese shipbuilding and remains the main plant of Mitsubishi Heavy Industries. His political-merchant management philosophy of 'developing together with the nation' has left its influence as one prototype of Japanese corporate governance.