The four largest ethnic groups reported in Didessa were the Oromo (90%), the Amhara (5.3%), the Kambaata (1.08%), and the Sebat Bet Gurage (0.99%); all other ethnic groups made up 2.63% of the population.
In Didessa, the Oromo were the predominant ethnic group at 90%, followed by the Amhara at 5.3%, Kambaata at 1.08%, and Sebat Bet Gurage at 0.99%. The remaining groups accounted for 2.63% of the population.