He was initially a disciple of the short-lived Darumashū sect of Japanese Zen founded by Nōnin,[1] but later studied and received dharma transmission under the Sōtō schools founder Dōgen.

[1] He is also featured prominently in the Denkōroku,[1] the first major piece of scripture produced in the Sōtō school after Dōgen, with his transmission story serving as the final koan.

He gave dharma transmission to Jakuen, Gikai, Gien and Giin, all of whom were originally students of Dōgen, but his failure to designate a clear heir himself led to a power struggle known as the sandai sōron that temporarily split the community.

[1] His teacher, Kakuan, a disciple of Nōnin,[3]: 8  had his community of monks in Tōnomine, outside Nara, apparently after having fled from Mount Hiei, where they had been persecuted by members of the Tendai school.

Following his master's death, Ejō left for Kannon-dōri-in (later changed to Kōshōhōrin-ji), Dōgen's newly established temple in Uji, where he would finally become his student.

Dōgen was reading a kōan to his students in which a monk asks Shishuang Chuyuan, "How is it that one hair digs many ditches"?, reportedly triggering his experience.

According to Dairyō Gumon, writing much later in the 17th century, Ejō received dharma transmission from Dōgen just after this event, complete with the presentation of certification documents.

Following these events, regardless of the veracity of Gumon's claims, contemporary historical sources such as the Denkōroku agree that Ejō was treated as Dōgen's heir, serving as his closest attendant.

Ejō apparently visited her during her illness during an allotted six-day vacation period following the winter sesshin, but shortly after he returned, he was informed his mother's condition had worsened and she would likely soon expire.

[2]: 128–129 In the summer of 1243, Ejō left Kōshōhōrin-ji for Echizen with Dōgen and his other students after Hatano Yoshishige, a magistrate from that area, offered land and protection for a new monastery.

[2]: 129 [3]: 30  Dōgen and his followers accepted the offer largely because of continuous tensions with the Tendai community in Kyoto which threatened the long-term stability of their practice.

[2]: 129 Ejō accompanied Dōgen to Kamakura, then the capital of Japan, during a six-month visit starting in 1247 on which he taught Hōjō Tokiyori, the shōgun's regent.

Dōgen left for Kyoto to seek medical assistance, but died a few days after his arrival there on 28 August, leaving Ejō as the sole leader of Eihei-ji.

Because Gikai had an interest in architecture and had recorded temple constructions during his time in China, Ejō allowed him to take control of the ongoing building projects at Eihei-ji.

After he died, confusion surrounded who should next lead the community, culminating in the climax of the sandai sōron, with several of Dōgen's students, especially Gikai and Gien, claiming the right to the abbotship.