The founding of Tohoku Gakuin dates back to 1886, when the private school "Sendai Theological Seminary" was established.

The 19th century was a time when various Christian denominations competed to send missionaries to Asia and Africa and begin evangelistic activities. In 1879, the first missionaries were sent to Japan from the German Reformed Church, and Christian evangelism began, mainly in Tokyo. Then, in December 1885, W.E. Hoy arrived in Japan as the third missionary from that denomination.

Meanwhile, Protestant Christianity was already beginning to take root in Japan around this time. Powerful missionary bases were established in Yokohama, Kumamoto, Sapporo, and other cities, producing many individuals who would play a leading role in Christian evangelism in Japan. One of them was Oshikawa Masayoshi, a former samurai of the Iyo Matsuyama domain. In 1872, while Christianity was still under prohibition, Oshikawa was baptized and became a member of Japan's first Protestant church. It was in 1880 that Oshikawa moved his base of operations to the Tohoku region. It was while Oshikawa was diligently continuing his missionary work, mainly in Sendai, that the aforementioned missionary, Hoy, arrived in Japan. Oshikawa, who had long hoped for the arrival of missionaries, met Hoy, who had just arrived in Japan, and secured a promise of cooperation. Young people seeking new knowledge gathered around Hoy, who had come from America. Then, in May 1886, a private school was opened in a rented house at the corner of Kimachi-dori and Kita-rokubancho, with six aspiring evangelists as students. This marked the birth of "Sendai Theological Seminary," the first step for Tohoku Gakuin.

Also that year, two female missionaries arrived in Sendai, and with the cooperation of Oshikawa, Hoy, and others, Miyagi Girls' School, the first girls' educational institution in Sendai—the current Miyagi Gakuin—was established.