She began the buildup to her 2010 World Cross Country campaign with wins at the Cross Internacional Valle de Llodio and Cross Internacional de Soria, beating the rest of the field by some distance both times. A win at the Cross Internacional de Itálica shortly after demonstrated her dominance of the Spanish circuit that year. At the 2010 World Cross Country Championships, she started strongly and began to build up a lead in the final lap. However, Emily Chebet overtook her with a sprint finish to the race, leaving Masai as the runner-up for the second time in as many years.