Tafari Benti was born near Addis Ababa. He joined the Ethiopian army at the age of 20, graduated from the Holetta Military Academy, and served in the Second, Third and Fourth Divisions. In 1967, he served as a military attaché in Washington, D. C., where he and several other Ethiopian colleagues suffered from racial discrimination.
On the evening of 23 November 1974, the charismatic Lt. General Aman Mikael Andom, the president of Ethiopia, and who had been in a struggle for power with the other members of the Derg, was killed in a shootout at his home. Mengistu Haile Mariam served as interim president until the Derg appointed Tafari Benti to the position. He had been serving as brigadier general in the Fourth Division, which was stationed in Asmara, at the time of this appointment.