Postol"s first significant title fight came in December 2011 against Karen Tevosyan for the vacant WBC Silver International light welterweight title. Before vacating the belt, Postol had managed to retain it against Ignacio Mendoza. Viktor Postol knocked out Lucas Matthysse in the 10th round for the vacant WBC light welterweight title at StubHub Center in Carson, California on October 3, 2015.
Postol managed to win via unanimous decision to claim the belt. After vacating the belt, Postol met in the ring with American Hank Lundy for the vacant WBC International light welterweight title and achieved a victory. In May 2014, Postol defeated Turkish boxer Selçuk Aydın in WBC title eliminator and earned a mandatory title shot against champion Danny García.
He then successfully defended it against Yvan Mendy and DeMarcus Corley.
