In the final competition, broadcast internationally on May 28, 2007, Mori was announced as one of fifteen semi-finalists who would move forward to compete for the title. She achieved the highest score in the swimsuit competition, which advanced her to the top ten and the evening gown competition, in which she placed fourth. Mori's kimono-inspired black/floral evening gown of choice came from the Spring/Summer 2007 collection of Gucci.

In the last round, Mori was asked by ELLE Magazine fashion director and Project Runway judge, Nina Garcia, to speak about the one lesson she learned as a child that still affects her life to the present day. Mori said that since childhood she has been dancing and hence she was constantly surrounded by students and teachers. Due to the interactions with them, she has learned to become always happy, patient, and positive in her life. She also expressed a desire to teach these principles to the next generation.

At the conclusion of the competition, she was crowned Miss Universe, becoming the second woman from Japan to hold the title. The first Miss Universe winner from Japan was Akiko Kojima in 1959. Mori is the ninth Asian woman to win the pageant, the most recent being Lara Dutta of India who was Miss Universe 2000.