Nichiji was born in Suruga Province, the second child of a large and powerful family. At first he studied to become a Tendai priest but soon he joined Nichiren as one of his initial followers.
Nichiji was one of the "six chosen disciples" of Nichiren, but was also a disciple of Nikkō. After Nichiren died in 1282, Nichiji established Eishō-ji, now Ren'ei-ji (蓮永寺) in Shizuoka. But soon, relations with Nikkō became strained. He set out on a missionary journey on January 1, 1295. His plan was to walk to Hakodate, Hokkaidō and from there proceed to Xanadu in order to convert the Mongols. While the Mongols appear frequently in Nichiren's writings as a fearsome force which Japan must tame, little was known about them and the city of Xanadu was just as mysterious in Japan as it seems to us today.
For many centuries it was unknown what happened to Nichiji after he left Japan. According to legend, he founded a temple in northern Japan and caught a new fish in Hokkaido that he named hokke, after the Lotus Sutra(法華,hokke?); even in legends it was unclear if he ever reached China alive. In 1936, though, a Japanese tourist discovered his gohonzon and relics in a remote region of China, and in 1989 these relics were carbon dated and determined by Tokyo University researchers to be most probably authentic. Thanks to his inscriptions on the relics, it is now known that he landed in China in 1298, met some Western Xia Buddhists on the road and decided on their advice to settle in Xuanhua District instead of Xanadu. In Xuanhua, he founded Lìhuà Temple (立化寺塔; Japanese: Rikkai-ji)., and a few Chinese residents converted to Nichiren Buddhism under his tutelage, including an old man named Nishote whom he mentions as his chief disciple. He died sometime after 1304.
In Nichiren Shū Nichiji is regarded as a patron saint of foreign missionaries.