Like his younger brother Izates bar Monobazus and his mother, Monobazus became a convert to Judaism. He ruled as king of Adiabene after the death of his brother Izates around 55 CE. The date of his death is unknown but he is known to have been alive and on the throne during the First Jewish-Roman War, when he gave aid to the Jewish rebels against the Roman Empire. Two 'kinsmen' of Monobazus, Monobazus and Kenedaeus, fought on the side of the Jews in the battle against Cestius. And the 'sons and brothers of Izates the king' were taken hostage to Rome after the war. The latter quotation suggests that Monobazus II was also called Izates, like his brother. Josephus Flavius says that the leaders of the Jewish Revolt were crucified, which may have included Monobazus II; he took three of them down from the cross and one of them survived.
The Talmud relates that Monobazus: "dissipated all his own hoards and the hordes of his fathers in years of scarcity. His brothers and his father's household came in a delegation to him and said, 'Your father saved money and added to the treasures of his fathers, and you are squandering them.' He replied, 'My fathers stored up below and I am storing up above... My fathers stored in a place which can be tampered with, but I have stored in a place which cannot be tampered with … My fathers gathered treasures of money and I have gathered treasures of souls...' " King Monobaz also donated handsome gifts to the Temple in Jerusalem. "King Monobaz had all the handles of all the vessels used on Yom Kippur made of gold … He also made of gold the base of the vessels, the rims of the vessels, the handles of the vessels, and the handles of the knives..."
Queen Helena of Adiabene was also said to be the wife of King Abgarus of Edessa and thus she was also the queen of Edessa. This implies that Monobazus II became the king of both Adiabene and Edessa, and so may well be cognate with Manu VI of Edessa. Moses of Chorene confirms that this Queen Helena of Edessa was also the queen of Adiabene when he says:
- "The chief of King Abgar’s wives, who was named Helena ... Helena went away to Jerusalem in the time of Claudius, during the famine which Agabus had predicted. Spending all her treasures she bought an immense amount of grain in Egypt, which she distributed to the poor, to which Josephus bears witness. Her famous mausoleum stands before the gate at Jerusalem to this very day."
- Josephus, War 2:19:2
- Josephus, War 6:6:4
- Josephus, Life 75.
- Baba Batra 11a.
- Yoma 37a,b.
- The Sociology of MMT and the Conversions of King Abgarus and Queen Helena of Adiabene, Professor Robert Eisenman.
- Moses of Chorene, History of the Armenians 2:35