Mucianus served as governor of Syria in 67 AD, following the outbreak of the Jewish revolt during the previous year. The future emperor Vespasian had been sent on a special mission to Judaea in 66 AD to put down the revolt. Initially, Mucianus and Vespasian were poorly disposed towards one another, however the feud was resolved by the beginning of 69. After the death of Galba, Mucianus and Vespasian both swore allegiance to Otho, but when the civil war broke out, Mucianus persuaded Vespasian to take up arms against Vitellius, who had seized the imperial throne.