Although little is known about him, he appears in the Books of Chronicles, and in the Book of Zechariah as Zechariah's grandfather. In the Books of Chronicles, the Chronicler states that the events of Solomon's reign, as well as Iddo's prophecies concerning the rival king Jeroboam I of Israel were recorded in writing. The alleged records composed by Iddo are no longer extant. He is also credited with a history of King Rehoboam, and a history of his son King Abijah.
A tradition of identifying Iddo with the unnamed prophet of 1 Kings 13 can be found in the Talmud, first-century CE Jewish historian Josephus, the fourth- and fifth-century Christian commentator Jerome, and the medieval Jewish commentator Rashi. The protagonist of 1 Kings 13 is identified simply as "a man of God" who prophesies against Jeroboam, as Iddo is said to have done elsewhere. After an unfortunate encounter with an older prophet of Bethel who lies to him, saying that God's angel has instructed him to provide hospitality to him, the "man of God" is killed by a lion as punishment for unwittingly disobeying a divine command. The older prophet, also unnamed, then used his own tomb as a burial place for the "man of God". The second Book of Kings records that, 300 years later, during the reign of king Josiah, the king was engaged in the process of burning human bones to ritually defile Jeroboam's altar. During the trip to do so, Josiah noticed the tombstone of the "man of God", and when he asked was told that it was the tomb of the man who had predicted the destruction of Jeroboam's altar. Josiah ordered that the tomb be left unmolested in commemoration of his prophecy.
Another Iddo is mentioned in Ezra 8:17 as the chief man at the place Casiphia. Ezra requests assistance from Iddo and his brethren to bring servants for the Temple. It is this Iddo to whom Ezra refers when he calls the prophet Zechariah a "son of Iddo" in Ezra 5:1 and 6:14. The Book of Zechariah 1:1 and 1:7 mention Iddo as the paternal grandfather of Zechariah.