Tadamune was born as Torakikumaru (虎菊丸) later Sōjirō (総次郎) the second son of Date Masamune. Although he was the second son, his elder half-brother Date Hidemune was born by Lady Iisaka, a concubine, and was thus not eligible to rule. At the age of seven, he was betrothed to Ichi-hime, the 5th daughter of Tokugawa Ieyasu; however, she died three years later, and he was betrothed again to the daughter of Ikeda Terumasa, who was also Ieyasu's grand-daughter. In 1611, shōgunTokugawa Hidetada presided over his genpuku ceremony, and he received courtesy title was Mimasaka-no-kami, and Senior Fifth Rank, Lower Grade Court rank. He also received permission from the shōgun to use the Matsudaira surname as an honorific.
At the time of the 1614 Siege of Osaka, he accompanied his father in the train of Tokugawa Ieyasu, and it was by order of Ieyasu that Date Hidemune was ordered to establish an independent branch of the Date clan at Uwajima in Shikoku with a kokudaka of 100,000 koku, whereas Date Tadamune was confirmed as heir to the main Date line at Sendai.
Tadamune was elevated to Junior Fourth Rank, Lower Grade, and given the honorary title of chamberlain in 1616. In 1624, his courtesy title was changed to Echizen-no-kami, and changed again in 1626 to Sakonoe-gon-shōshō (General of the Left Guards).
On Masamune's death in June 1636, he became daimyō, and entered Aoba Castle in Sendai for the first time in August of the same year. He immediately took over the reins of government by replacing two of the six bugyōs, and re-establishing a multi-person system of magistrates and inspectors to provide more oversight and to eliminate corruption and arbitrary rule. He followed this the following year by publishing a new code of rules and regulations for the domain. In 1639, his courtesy title was changed to Mutsu-no-kami.
In terms of finances, from 1640 to 1643 he ordered a complete re-survey of the domain, bringing units of measurements in line with the nation-wide standards used by the Tokugawa shogunate. This was accompanied by large scale land reform. Tadamune also established a system whereby the domain purchased all rice produced in the domain, and reselling in Edo, paying the farmers in advance. This encouraged the opening of new rice lands.
During Tadamune's tenure, Sendai Castle was completed, and he sponsored the construction of numerous temples and shrines, including the Zuihōden in 1637 and the Sendai Tōshōgū in 1654.
On Tadamune's death on 12 July 1658, one of his senior retainers, Furuuchi Shigehiro, committed ritual suicide (junshi). Tadamune's sixth son Date Tsunamune became daimyō of Sendai.
