別府大分毎日マラソン
The third marathon win of Kosgei's career came in February 2010 at the Beppu-Ōita Marathon, as he outran second-placed Daniel Njenga as the course entered the final straight at Ōita Stadium. He ran in the Kenya National Cross Country Championships that month but he was ninth and did not gain selection for the world championships. An appearance at the São Paulo International Marathon saw him finish as runner-up behind Stanley Biwott. Kosgei was the pre-race favourite for the Athens Classic Marathon, a competition celebrating 2500 years since the Battle of Marathon, but he was beaten by Raymond Bett and ended up second past the post.