Dergo's compatriot Meseret Kitata Tolwak grabbed the silver medal in 2:31:08. Gong Lihua of China came third in 2:32:23, while defending champ Zhang Yingying was fourth in 2:37:09.
"It's a little cool today, and my muscle felt stressed," said Gong.
Since 1992, Chinese women runners never let the title slip away. But Dergo turned a new page.
Girmay Birhanu Gebru of Ethiopia won the men's event in two hours, ten minutes and 42 seconds.
Gebru had hoped to break the tournament record of 2:07:16, set by Ethiopian Tadese Tola one year ago, but it turned out to be almost five minutes shy of his personal best (2:05:49).
"It was a tough game, but I was satisfied with what I did to finish the match. Looking forward to coming back to Beijing next year," said Gebru.
The second and third place went to Abebe Negewo Degefa of Ethiopia (2:10:54) and Solomon Bushendich Naibei of Kenya (2:11:07) respectively.
The organizers adjusted the race events and slots allocation with the mini marathon event being cancelled in 2014. The full-race marathon was open to 26,000 entrants and half marathon to 4,000.