Dejen is the latest in the line of young, spectacular athletes coming out of Ethiopia today, putting themselves atop of the world distance running charts. Like double 1980 Olympic champion Miruts Yifter and New York Marathon Champion Gebre Gebremariam, Dejen hails from Ethiopia's northern Tigray Region, where he first began to compete in local championships, before being recruited to train with the national team in Addis Ababa.

Dejen took silver at his first international championships, placing second in the 5000m at the 2007 African Junior Championships. A year later, he won the bronze medal over 5000m at the World Junior Championships in Poland. Since transitioning from the junior to senior ranks, Dejen has established himself as one of Ethiopia's best distance runners; he was Ethiopia's fastest 5000m for 2010, and secured podium finishes at major invitationals in Boston, Oregon and Stockholm.