Mulatu was born in the town of Arjo in Welega Province. He was educated in China, receiving his bachelor's degree in philosophy of political economy and doctorate in international law at Peking University. He received his Master of Arts in Law and Diplomacy from The Fletcher School of Law and Diplomacy at Tufts University in 1990. He taught at some "foreign universities and institutions", according to Speaker Abadula Gemeda.
In the mid-1990s he was Deputy Minister of Economic Development and Cooperation under Minister Girma Birru, and he was appointed as Minister of Agriculture in 2001.He was also Speaker of the House of Federation from 2002 to 2005 He served as Ethiopia's Ambassador to China, Japan, Turkey, and Azerbaijan.
While serving as Ambassador to Turkey, he was elected as President of Ethiopia by a unanimous parliamentary vote on 7 October 2013. Girma Seifu of the Unity for Democracy and Justice, the sole opposition member of parliament, welcomed his election. Like his predecessors Girma Wolde-Giorgis and Negasso Gidada, he is Oromo.