He belonged to a family of Malla chieftains and was educated at Takkasilā, where he attained great proficiency. Later, while journeying in the company of Sabhiya, he came to Sāvatthi, where he was present at the discussion between Sabhiya and the Buddha. It was his purpose to try and discover flaws in the Buddha's argument. The Buddha knew what was in his mind, and at the end of the Sabhiya Sutta admonished him in five verses (Thag.360 4). Yasadatta was greatly moved and entered the Order, winning arahantship in due course.
In the time of Padumuttara Buddha, he had been a very learned brahmin, living as an ascetic in the forest. One day he saw the Buddha, and, with clasped hands, praised his virtues (Thag.i.427f).
He is evidently identical with Ñānathavika of the Apadāna. (Ap.ii.392f)