He belonged to a brahmin family and studied under Bāvarī as an ascetic. He was one of the sixteen pupils sent by Bāvarī to the Buddha. When Mogharāja had asked his question of the Buddha and had received the answer, he attained arahantship. He then attained distinction by wearing rough cloth which had been thrown away by caravaners, tailors, and dyers, and the Buddha declared him foremost among wearers of rough clothing (See also A.i.25). Later, through want of care and former kamma, pimples and the like broke out over his body. Judging that his lodging was infected, he spread a couch of straw in the Magadha field and lived there even during the winter. When the Buddha asked him how he fared in the cold, he replied that he was extremely happy (Thag.207f).
In the time of Padumuttara Buddha, Mogharāja first resolved to win the eminence which was his. In the time of Atthadassī Buddha he was a brahmin teacher, and one day, while teaching his students, he saw the Buddha, and having worshipped him with great solemnity, he uttered six verses in his praise and offered him a gift of honey. Later, after sojourn in the deva worlds, he became a minister of King Katthavāhana, and was sent by him, with one thousand others, to visit Kassapa Buddha. He heard the Buddha preach, entered the order, and lived the life of a monk for twenty thousand years (ThagA.i.181ff.; SN. vs. 1006). The Samyutta Nikāya contains a stanza spoken by Mogharāja and the Buddha's answer thereto (S.i.23).
Buddhaghosa explains (SA.i.49f) that Mogharāja was present during the discussion of Pasuraparibbājaka (q.v.) with Sāriputta. At the end of Sāriputta's explanation, Mogharāja wished to settle the matter and uttered this stanza.
Mogharāja is given as an example of one who attained arahantship by the development of investigation (vimāmsam dhuram katvā) (SA.iii.201).
The Apadāna contains two sets of verses in reference to Mogharāja. They seem to be parts of the same Apadāna which have become separated. The first set (Ap.i.87f ) gives an account of the meeting of Mogharāja with Atthadassī Buddha (see above) and includes the verses uttered by Mogharāja in praise of the Buddha. The second set (Ap.ii.486f) contains an account of his meeting with Padumuttara Buddha and the resolves he made before him. It further mentions that, for one thousand years, in a later birth, Mogharāja suffered in hell, and that for five hundred births he suffered from skin diseases. This was because he had lighted a fire in the Buddha's cloister and had made the floor black. In his last birth, too, he suffered from a kuttharoga and could not sleep at night, hence his name (mogharajjasukham yasmā Mogharājā tato aham). These verses also include the Mogharājamānava pucchā.
In the Milinda-Pañha (p. 412) appears a stanza attributed to Mogharāja, but not found in the stanzas mentioned in connection with him either in the Sutta Nipāta or in the Theragāthā. See also Mogharā-jamānava-pucchā.