Mekhontsev then moved up to the heavyweight 201 lbs limit division and won the 2008 Russian national championships beating Evgeniy Romanov in the final by a score of 19–5.

[4] [5] At the 2009 World Amateur Boxing Championships – Heavyweight he upset Clemente Russo and beat fellow southpaws Oleksandr Usyk in the semifinal and Osmay Acosta in the final.

He beat Marcus Browne and Oleksandr Hvozdyk but was upset by young Cuban Julio César la Cruz and won Bronze.

At the 2012 Olympics, being 28 years of age, he beat Damien Hooper, Elshod Rasulov, Yamaguchi Falcao in the semifinals and won Gold by defeating Adilbek Niyazymbetov.

[7] Mekhontsev made his professional debut on December 7, 2013, dominating and knocking down opponent PJ Cajagas three times before the referee stopped the contest in the third round.