Born in 1836 in the village of Beryoza, Smolensk Governorate, Russian Empire. His original name was Ivan Dmitrovich Kasatkin. While a student at the St. Petersburg Theological Academy, he volunteered for missionary work in Japan, became a monk, and received the name Nicholas. In 1861 he came to Japan as the priest attached to the Russian consulate in Hakodate. His first convert was Sawabe Takuma, priest of the Hakodate Shinmei shrine (a cousin of Sakamoto Ryoma). In 1872 he moved his base to Tokyo and bought land on the height at Surugadai. In 1891 he completed the Cathedral of the Holy Resurrection in Tokyo (Nikolai-do), the most magnificent Orthodox building in Japan. In 1880 he was consecrated bishop by the Russian Orthodox Church, and in 1907 was raised to the rank of archbishop. Even during the Russo-Japanese War (1904–05) he deliberately remained in Japan, continuing to comfort Russian prisoners of war and to translate scripture, and guarding the trust of his Japanese faithful to the end. In his fifty-one years in Japan he translated into Japanese the whole of the Old and New Testaments and a great body of religious writings besides, and raised up some 33,000 faithful and more than 260 parish communities. He died in Tokyo in 1912 at the age of 75. In 1970 he was canonized by the Russian Orthodox Church as 'Saint Nicholas, Equal-to-the-Apostles of Japan.'

A taciturn and enduring priest. He loved Japanese culture to the point of saying 'I wish to become a Japanese' and spoke fluent Japanese. During the Russo-Japanese War, as a Russian priest he would not offer prayers for victory before his Japanese faithful, yet did not miss a single day in offering prayers in the name of the Russian emperor. That strict sincerity brought still greater devotion from his Japanese flock. Believing that 'the Orthodox Church of Japan should be run by Japanese hands,' he poured his strength into training Japanese priests.

The Cathedral of the Holy Resurrection was damaged in the Great Kanto Earthquake but was rebuilt, and remains a landmark of Ochanomizu today. The Orthodox Church in Japan, with 40,000 faithful at its prewar peak, continues even now as Japan's only autonomous Orthodox Church. Nicholas's principles of scripture translation and evangelism are carried on in the current Japanese-language Orthodox Bible. The way he spent half a century in a foreign culture and, even when his country became the enemy, guarded his faithful to the end is esteemed worldwide as a case without parallel in the history of modern mission.