Light-Heavyweight

Southpaw Mekhontsev won a silver medal in the 2004 Light-heavyweight Russian senior national championships losing to Mikhail Gala in the final and won another silver in 2005 again losing to Gala in the semi-final by 39:26.

The following year in 2006 he won bronze losing to Artur Beterbiyev 41:30 in the semi-final and in 2007 another bronze losing to Evgeni Makarenko.

Change to Heavyweight

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.^[3]

At the 2008 European Amateur Boxing Championships in Liverpool he defeated Nasi Hani (Macedonia) INJ RND 4, Stephen Simmons (boxer) (Scotland) 14–1, Petrisor Gananau (Romania) 5–2 and won Gold after defeating Armenia's Tsolak Ananikyan 9–2 in the final.^{[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.

Mekhontsev successfully defended his title at the 2010 European Amateur Boxing Championships against Denis Poyatsika and Tervel Pulev.^[6]

Change to Light-Heavyweight

For the 2011 World Amateur Boxing Championships he traded weightclasses with Beterbiyev and dropped to light heavy. 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.

Turning professional

Mekhontsev turned professional in October 2013, signing with boxing promotion company Top Rank, which has also signed up a number of other 2012 olympic medallists.^[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.